Abstract:
Lost circulation materials and methods for maintaining emulsion stability in emulsion type drilling, drill-in, and completion fluids, particularly invert emulsions.

Description:
[0001]    The present application claims the benefit of U.S. Provisional Application Serial No. 60/315,761, filed Aug. 29, 2001, pending. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to lost circulation materials, and to methods for maintaining emulsion stability in emulsion type drilling, drill-in, and completion fluids (hereinafter sometimes collectively referred to as “drilling fluids”) containing lost circulation material(s).  
         BACKGROUND OF THE INVENTION  
         [0003]    Drilling fluids serve various functions, such as promoting borehole stability, removing drilled cuttings from the wellbore, cooling and lubricating the bit and the drillstring, as well as controlling subsurface pressure. Certain subsurface conditions can cause, or lead to, “loss of circulation,” or the loss of whole drilling fluid in quantity to the formation. Examples of such subsurface conditions include, but are not necessarily limited to: (1) natural or intrinsic fractures, (2) induced or created fractures; (3) cavernous formations (crevices and channels), and (4) unconsolidated or highly permeable formations (loose gravels).  
           [0004]    Lost circulation materials are used to minimize loss of circulation. The lost circulation material forms a filter cake that effectively blocks voids in the formation. Currently, lost circulation materials include fibrous materials, such as cedar bark and shredded cane stalk, flaky materials such as mica flakes, and granular materials such as ground limestone, wood, nut hulls, corncobs, and cotton hulls.  
           [0005]    Unfortunately, low electrical stability values have been reported for invert emulsion drilling fluids containing fibrous cellulosic lost circulation material. If the electrical stability value of a drilling fluid becomes too low, water wetting of solids occurs, which may cause the rheological properties of the fluid to break down, rendering the drilling fluid ineffective and even resulting in a shutdown of drilling operations.  
           [0006]    Lost circulation materials and methods of use are needed which maintain electrical stability, and thereby emulsion stability of drilling fluids.  
         SUMMARY OF THE INVENTION  
         [0007]    The invention provides a method for maintaining electrical stability in a drilling, drill-in, or completion fluid comprising lost circulation material (LCM), said method comprising:  
           [0008]    providing an initial fluid selected from the group consisting of a drilling, drill-in, or completion fluid, said initial fluid having effective rheology and fluid loss control properties;  
           [0009]    adding to said initial fluid a fibrous LCM consisting essentially of a quantity of high lignin lost circulation material (HLLCM), thereby producing a treated fluid.  
           [0010]    In another aspect, the invention provides a method for maintaining electrical stability in a drilling, drill-in, or completion fluid, said method comprising:  
           [0011]    providing an initial fluid selected from the group consisting of a drilling, drill-in, or completion fluid having effective rheology and fluid loss control properties; and  
           [0012]    using as LCM in said initial fluid a fibrous HLLCM having a water retention value of about 1 or less.  
           [0013]    In yet another aspect, the invention provides a method for maintaining electrical stability in a drilling, drill-in, or completion fluid, said method comprising:  
           [0014]    providing an initial fluid selected from the group consisting of a drilling, drill-in, or completion fluid, said initial fluid having effective rheology and fluid loss control properties; and  
           [0015]    using grape pumice as a lost circulation material.  
           [0016]    In preferred embodiments, said initial fluid exhibits a first electrical stability value and said treated fluid exhibits a second electrical stability value that is a maximum of 18% less than said first electrical stability value; more preferably 15% less than said first electrical stability value; most preferably 12% less than said first electrical stability value. The initial fluid preferably is an emulsion base fluid, most preferably an invert emulsion fluid. The fibrous HLLCM preferably has a water retention value of about 1 or less, more preferably about 0.5 or less, even more preferably about 0.3 or less. Preferred HLLCM&#39;s are selected from the group consisting of grape pumice, bulrush plants, and lignin byproducts from processing plant material into paper. A most preferred HLLCM is grape pumice. The HLLCM preferably comprises a particle size distribution of from about 10 μm to about 200 μm.  
           [0017]    In another aspect, the invention provides a fluid selected from the group consisting of a drilling, drill-in, or completion fluid having effective rheology and fluid loss control properties and comprising a lost circulation material consisting essentially of an HLLCM.  
           [0018]    In another aspect, the invention provides a fluid selected from the group consisting of a drilling, drill-in, or completion fluid, said fluid having effective rheology and fluid loss control properties and consisting essentially of an LCM having a water retention value of about 1 or less.  
           [0019]    In another aspect, the invention provides a fluid selected from the group consisting of a drilling, drill-in, or completion fluid, said fluid having effective rheology and fluid loss control properties and comprising a fibrous LCM, said fibrous LCM consisting essentially of materials selected from the group consisting of grape pumice, bulrush plants, and lignin byproducts from the processing of plant material into paper.  
           [0020]    In yet another aspect, the invention provides a fluid selected from the group consisting of a drilling, drill-in, or completion fluid, said fluid having effective rheology and fluid loss control properties and comprising a fibrous LCM consisting essentially of grape pumice.  
           [0021]    In preferred embodiments, the initial fluid exhibits a first electrical stability value and a fluid comprising said HLLCM exhibits a second electrical stability value that is a maximum of 18% less than said first electrical stability value; more preferably 15% less than said first electrical stability value; most preferably 12% less than said first electrical stability value. The initial fluid preferably is an emulsion base fluid, most preferably an invert emulsion fluid. The fibrous HLLCM preferably has a water retention value of about 1 or less, more preferably about 0.5 or less, even more preferably about 0.3 or less. Preferred HLLCM&#39;s are selected from the group consisting of grape pumice, bulrush plants, and lignin byproducts from processing plant material into paper. A most preferred HLLCM is grape pumice. The HLLCM preferably comprises a particle size distribution of from about 10 μm to about 200 μm.  
           [0022]    In yet another aspect, the invention provides a spotting pill comprising from about 1 to about 100 ppb of an HLLCM and a carrier liquid. Preferably, the spotting pill comprises from about 5 to about 50 ppb of an HLLCM and a carrier liquid.  
           [0023]    The HLLCM preferably consists essentially of materials selected from the group consisting of grape pumice, bulrush plants, and lignin byproducts from the processing of plant material into paper. In a most preferred embodiment, the HLLCM is grape pumice.  
           [0024]    In yet another aspect, the invention provides a spotting pill comprising from about 1 to about 100 ppb grape pumice a carrier liquid, preferably from about 5 to about 50 ppb of grape pumice and a carrier liquid.  
           [0025]    The carrier liquid preferably is selected from the group consisting of a polyalkylene oxides and copolymers thereof, polyalkyleneoxide glycol ethers, glycols, polyglycols, tripropylene glycol bottoms, and combinations thereof. In a preferred embodiment, the carrier liquid is selected from the group consisting of ethylene glycols, diethylene glycols, triethylene glycols, tetraethylene glycols, propylene glycols, dipropylene glycols, tripropylene glycols, tetrapropylene glycols, polyethylene oxides, polypropylene oxides, copolymers of polyethylene oxides and polypropylene oxides, polyethylene glycol ethers, polypropylene glycol ethers, polyethylene oxide glycol ethers, polypropylene oxide glycol ethers, and polyethylene oxide/polypropylene oxide glycol ethers. In another preferred embodiment, the carrier liquid is selected from the group consisting of ethylene glycol, tripropylene glycol bottoms, and combinations thereof.  
           [0026]    In a most preferred embodiment, the carrier liquid comprises tripropylene glycol bottoms. In a most preferred embodiment, the HLLCM is grape pumice, most preferably combined with tripropylene glycol bottoms. Where alkalinity of the drilling fluid is a concern, the pH may be maintained by using about 0.2 lb soda ash to about 1 lb grape pumice, in the spotting additive, or during mixing. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]    [0027]FIG. 1 is a graph showing comparative LCM effects upon electrical stability in a field ECO-FLOW sample.  
         [0028]    [0028]FIG. 2 is a graph showing a particle size distribution analyses of CHECK-LOSS® in various fluids. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0029]    Measurements of an emulsion-type drilling fluid are continually made in an effort to identify any loss in emulsion stability resulting from loss of circulation of the drilling fluid. A preferred method of measuring emulsion stability in invert emulsion drilling fluids is to measure the electrical stability of the drilling fluid.  
         [0030]    The electrical stability of an oil-based drilling fluid relates both to its emulsion stability and to its oil-wetting capability. Electrical stability of a drilling fluid is determined by applying a voltage-ramped, sinusoidal electrical signal across a pair of parallel flat-plate electrodes immersed in the drilling fluid. The resulting current remains low until a threshold voltage is reached, whereupon the current rises very rapidly. This threshold voltage is the electrical stability of the drilling fluid and is defined as the voltage in peak volts-measured when the current reaches 61 μA.  
         [0031]    Field operators monitor the emulsion stability of a drilling fluid by reading the voltage across the drilling fluid. The resulting electrical stability reading is directly related to the ratio of water to oil in a particular drilling fluid. As the concentration of water in the drilling fluid increases, the electrical stability value tends to decrease.  
         [0032]    The reported decrease in electrical stability values in invert emulsion drilling fluids appears to be attributable to swollen, hydrated fibers of lost circulation material that come into contact with the electrical stability meter probe. In order to preserve electrical stability (and thereby emulsion stability), water wetting of such fibrous materials must be minimized.  
         [0033]    The type of lost circulation material added to a particular drilling fluid varies according to the primary purpose of the drilling operation; the nature of the rocks to be penetrated; the site, and the skill and experience of the drilling crew. Various plant source fibers are used as lost circulation materials. Cellulose is a major constituent of most plant cell walls, and also has a high affinity for water. Without limiting the invention to a particular mechanism of action, the decrease in electrical stability of drilling fluids comprising many fibrous lost circulation materials is believed to be due to the intrinsic affinity of the cellulose in those fibers for water. In order to reduce the impact of a lost circulation material on electrical stability readings, the present invention reduces the cellulosic content of the fibrous material.  
         [0034]    Lignin also is found in plant cell walls. Lignin is a strengthening polymer which provides rigidity and strength to the plant material. Lignin does not have as great an affinity for water as cellulose. Plant materials with higher lignin contents should have a directly or indirectly proportional decrease in affinity for water. It is difficult to analyze plant materials directly to determine their lignin content.  
         [0035]    The present invention involves the use of “high lignin” lost circulation materials (HLLCM&#39;s) in drilling fluids. HLLCM&#39;s increase electrical stability values in emulsion type fluids, and thereby increase emulsion stability. “HLLCM&#39;s” are herein defined as fibrous lost circulation materials effective to maintain the electrical stability value of a given drilling, drill-in or completion fluid to within 20% or less of the electrical stability value of the same fluid in the absence of the HLLCM. Preferred HLLCM&#39;s are effective to maintain the electrical stability value of a given drilling, drill-in or completion fluid within 18% of the electrical stability value of the same fluid in the absence of the HLLCM, more preferably to within about 15%, and most preferably to within about 12%. Another way of stating the electrical stability limitation is that the addition of the HLLCM causes a maximum reduction in voltage reading of 20% or less relative to the initial voltage reading, more preferably about 18% or less, even more preferably about 15 % or less, most preferably about 12% or less.  
         [0036]    Suitable HLLCM&#39;s may be identified with reference to their “Water Retention Value” (WRV). A given plant material has a given hydration rate based on the size of voids within the fibers of that plant material. When the dry plant material is exposed to water, these voids are swollen by the water. The swelling of these voids in the presence of water may be measured, and the measured value is known as the material&#39;s WRV. The WRV is a measure of the amount of water intimately associated with a given dry weight of a given plant material, and is approximately equal to the total change in volume of the cell wall of the plant material.  
         [0037]    The WRV for a given plant material may be calculated upon performing a simple test. Add 25 g test material to a glass jar. Mix 250 ml of deionized water with the test material. Shear the slurry at 3000 rpm for 5 min. Cap the glass jar roll 16 hr at 150° F. After cooling, pour the jar contents into an assembled Buchner funnel (using Whatman filter paper No. 41) fitted on a 2-liter Erlenmeyer flask, hooked to a vacuum pump. Filter for two hours maximum. Remove the Buchner funnel with test material from the flask and weigh. Calculate the WRV using the following equation:  
         (Buchner funnel with filter (Buchner funnel with wet paper)−paper and retained wet test material)/Initial 25 g dry test material.  
         [0038]    Fibrous lost circulation materials in current use have a calculated WRV of about 4 or more. HLLCM&#39;s that are suitable for use in the present invention have a calculated WRV of 1 or less, preferably 0.5 or less, and more preferably 0.3 or less.  
         [0039]    Examples of suitable HLLCM&#39;s include, but are not necessarily limited to plants that actually grow in water but tend to remain dry, such as bulrush plants, which include cattails, papyrus, and the like. Also suitable are lignin byproducts derived from the processing of wood or other plant materials into paper. The products made from such processes typically require high contents of cellulose, and lignin is processed out of the wood. The lignin typically is sold for sulfonation.  
         [0040]    The HLLCM generally has a particle size distribution effective to form a filter cake and to block loss of circulation of the drilling fluid to the formation. Suitable particle size distributions generally are from about 10 μm to about 200 μm, preferably from about 15 to about 170.  
         [0041]    A most preferred HLLCM for use in the invention is grape pumice. HLLCMs, preferably grape pumice, have the added advantage of inducing less impact upon rheological properties.  
         [0042]    The HLLCM preferably is used in emulsion type drilling fluids, most preferably invert emulsion drilling fluids. However, HLLCM&#39;s are useful as a lost circulation materials in any type of drilling fluid, including water base fluids, natural or synthetic oil base fluids, oil-in-water emulsion fluids, and water-in-oil emulsion fluids.  
         [0043]    The HLLCM may be included as an integral part of a drilling fluid, and/or added to a drilling fluid, as needed, during drilling operations. Where the HLLCM is used as an integral part of a drilling fluid, the quantity used is from about 0.1 ppg to about 25 ppg, preferably from about 5 ppg to about 10 ppg. Where the HLLCM is added to the drilling fluid as needed during operation, the HLLCM is simply added to the mud pit with mixing, as needed. The quantity of HLLCM added will vary depending upon the extent of the loss in circulation. Typically, the quantity is from about 0.1 ppg to about 25 ppg or more.  
         [0044]    Alternately, the HLLCM is added to the mud pit as a spotting pill. In this embodiment, the HLLCM is added as a slurry, together with a small amount of a carrier liquid that is compatible with the fluid being treated. A preferred slurry comprises from about 1 ppb to about 100 ppb HLLCM, preferably about 5 to about 50 ppb HLLCM. A most preferred spotting pill is from about 1 ppb to about 100 ppb grape pumice in a carrier fluid, preferably from about 5 to about 50 ppb grape pumice. Typically, after the HLLCM is spotted opposite the loss zone, it is desirable to pull into the casing and wait six to eight hours before continuing operations.  
         [0045]    Whether used as a integral part of the drilling fluid, or in a spotting pill, certain HLLCM&#39;s, such as grape pumice, tend to increase the acidity of water base fluids. Hence, where the HLLCM is used in a water base fluid, it is preferred to add a sufficient quantity of a buffering agent to increase the pH to neutral, or about 7. Suitable buffering agents include but are not necessarily limited to soda ash, sodium bicarbonate, sodium hydroxide, lime, calcium hydroxide, and the like. A suitable amount of buffering agent is from about 0.1 lb to about 0.2 lb, preferably 0.1 lb, for every 10 lbs. HLLCM, preferably grape pumice.  
         [0046]    Suitable carrier fluids for a spotting pill vary depending upon the fluid being treated. Where the fluid is a water base fluid, the carrier preferably will be aqueous. Where the fluid is an oil base fluid, the carrier preferably will be non-aqueous, and so forth. In a preferred embodiment, the carrier fluid is selected from the group consisting of glycols, polyglycols, polyalkyleneoxides, alkyleneoxide copolymers, alkylene glycol ethers, polyalkyleneoxide glycol ethers, and salts of any of the foregoing compounds, and combinations of the foregoing compounds.  
         [0047]    Examples of suitable glycols and polyglycols include, but are not necessarily limited to ethylene glycols, diethylene glycols, triethylene glycols, tetraethylene glycols, propylene glycols, dipropylene glycols, tripropylene glycols, and tetrapropylene glycols. Examples of suitable polyalkyleneoxides and copolymers thereof include, but are not necessarily limited to polyethylene oxides, polypropylene oxides, and copolymers of polyethylene oxides and polypropylene oxides. Suitable polyalkyleneoxide glycol ethers include, but are not necessarily limited to polyethylene glycol ethers, polypropylene glycol ethers, polyethylene oxide glycol ethers, polypropylene oxide glycol ethers, and polyethylene oxide/polypropylene oxide glycol ethers. Preferred carriers are ethylene glycol, tripropylene glycol bottoms, and combinations thereof. A most preferred carrier is tripropylene glycol bottoms.  
         [0048]    The invention will be better understood with reference to the following Examples, which are illustrative only. In the examples, CHEK-LOSS® is a corn cob based LCM, available from Baker Hughes INTEQ; PHENO-SEAL® is a ground plastic resin material, available from Montello, Inc.; MUD-LINER is a paper based LCM, available from BCI Incorporated; LIQUID CASING is a peanut hull based LCM available from Liquid Casing, Incorporated; KWIK SEAL FINE is a blend of vegetable and polymer fibers available from Kelco Oilfield Group; and BAROFIBRE is an almond hull based LCM, available from Baroid/Halliburton.  
       EXAMPLE 1  
       [0049]    Field operations personnel reported continuing problems of low electrical stability values for invert emulsion drilling fluids containing fibrous lost circulation material (LCM) additives. Although not identifying the specific additives, a report indicated that all fibrous materials lowered electrical stability values. However, HPHT fluid losses of the laboratory test muds showed no evidence of water. The criteria of absence of water in the HPHT filtrate was used as the preferred method of determining emulsion stability.  
         [0050]    The following is an assessment of the effects of various LCM additives on electrical stability, Theological properties, and HPHT/PPA filtration control of synthetic-based fluids.  
         [0051]    Equipment  
         [0052]    1. Prince Castle mixer  
         [0053]    2. Fann viscometer, Model 35A  
         [0054]    3. Thermometer, dial, 0-220° F.  
         [0055]    4. Balance with precision of 0.01 g  
         [0056]    5. Sieves (conforming to ASTM E11 requirements)  
         [0057]    6. Roller oven, 150-250±5° F. (66-121±3° C.)  
         [0058]    7. Static aging oven  
         [0059]    8. Wash bottle  
         [0060]    9. Retsch grinding mill  
         [0061]    10. Mortar and pestle  
         [0062]    11. Spatula  
         [0063]    12. Timer: interval, mechanical or electrical, precision of 0.1 minute  
         [0064]    13. Jars (approximately 500 ml capacity) with sealing lids  
         [0065]    14. Heating cup, OFI, 115 volt  
         [0066]    16. Malvern Mastersizer  
         [0067]    Procedures  
         [0068]    The following INTEQ Fluids Laboratory procedures were used:  
         [0069]    Recommended Practice Standard Procedure for Field Testing Oil-Based Drilling Fluids, API Recommended Practice 13B-2, Third Edition, February 1998  
         [0070]    Recommended Practice Standard Procedure for Field Testing Water-Based Drilling Fluids, API Recommended Practice 13B-1, Second Edition, September 1997  
         [0071]    Instrumentation Manual for Malvern Mastersizer  
         [0072]    The following were the results  
                                                 TABLE 1                       Comparative evaluation of CHEK-LOSS ® and BLEN-PLUG OM in field SYN-TEQ ® samples                                Materials                                   SYN-TEQ (unknown LCM) Sample A, bbl   1.0   1.0   1.0   1.0   —   —   —       SYN-TEQ Sample B, bbl   —   —   —   —   1.0   1.0   1.0       CHEK-LOSS, Sample C, lb/bbl   —   10   —   —   —   10   —       BLEN-PLUG OM, Sample D, lb/bbl   —   —   10   —   —   —   10       Stirred 15 min   1290   1160   1040   1290   220   175   160       Electrical stability, volt       Rolled 16 hr, 150° F.       FANN 35 Properties:       600 rpm rdg, 120° F.   145   233   n/m   145   54   70   n/m       300 rpm rdg   82   131   —   82   30   39   —       200 rpm rdg   61   95   —   61   21   28   —       100 rpm rdg   38   58   —   38   13   17   —         6 rpm rdg   10   14   —   10   3   4   —         3 rpm rdg   8   11   —   8   2   3   —       Plastic viscosity, cp   63   102   —   63   24   31   —       Yield point, lb/100 ft 2     19   29   —   19   6   8   —       10-sec gel, lb/100 ft 2     10   12   —   10   3   5   —       10-min gel, lb/100 ft 2     13   16   —   13   5   7   —       Electrical stability, volt   1150   350   330   1150   220   150   130       60-mesh screened       ✓   ✓       Electrical stability, volt   —   390   350   —       Treatment:       Baroid DrilTreat, lb/bbl   5.0   5.0   5.0   —       INTOIL-S, lb/bbl   —   —   —   5.0       Electrical stability, volt   1290   385   350   1290       CHEK-LOSS, lb   10   —   —   10       Rolled 16 hr, 150° F.       Electrical stability, volt   430           440       600 rpm rdg, 120° F.   205           222       300 rpm rdg   118           129       200 rpm rdg   87           95       100 rpm rdg   54           60         6 rpm rdg   14           15         3 rpm rdg   11           12       Plastic viscosity, cp   87           93       Yield point, lb/100 ft 2     31           36       10-sec gel, lb/100 ft 2     15           16       10-min gel, lb/100 ft 2     18           19                  
 
         [0073]    [0073]                                                                                                                                                       TABLE 2                           Comparative evaluation of a) wetting agents with CHEK-LOSS ® in a field ECO-FLOW       and b) competitive fibrous LCM additives versus MIL-CARB ® or PHENO-SEAL                A: Wetting Agents with CHEK-LOSS   B: Fibrous LCM versus MIL-CARB                        Materials                                                           ECO-FLOW,   1.0   1.0   1.0   1.0   1.0   1.0   1.0   1.0   1.0   1.0   1.0   1.0   1.0       Sample E, bbl       DRILTREAT,   —   —   5.0   —   —   —   —   —   —   —   —   —   —       lb/bbl       INTOIL-S,   —   —   —   5.0   —   —   —   —   —   —   —   —   —       lb/bbl       BIO-COTE ™,   —   —   —   —   2.5   —   —   —   —   —   —   —   —       lb/bbl       OMNI-   —   —   —   —   —   2.5   —   —   —   —   —   —   —       COTE ®,       lb/bbl       CHEK-LOSS,   —   10   10   10   10   10   —   —   —   —   —   —   —       lb/bbl       PHENO-   —   —   —   —   —   —   10   —   —   —   —   —   —       SEAL, lb/bbl       LUBRA-   —   —   —   —   —   —   —   10   —   —   —   —   —       SEAL, lb/bbl       BAROFIBRE,   —   —   —   —   —   —   —   —   10   —   —   —   —       lb/bbl       MUD LINER,   —   —   —   —   —   —   —   —   —   10   —   —   —       lb/bbl       LIQUID   —   —   —   —   —   —   —   —   —   —   10   —   —       CASING,       lb/bbl       ULTRASEAL, lb/bbl   —   —   —   —   —   —   —   —   —   —   —   10   —       MIL-CARB,   —   —   —   —   —   —   —   —   —   —   —   —   10       lb/bbl       Stirred 15 min       Rolled 16 hr,       150° F.            Properties            600 rpm rdg,   122   178   155   168   153   150   125   136   157   198   165   160   124       120° F.       300 rpm rdg   72   100   88   95   80   80   73   79   90   112   94   90   73       200 rpm rdg   52   73   66   70   54   57   54   59   65   81   68   67   54       100 rpm rdg   33   45   41   43   30   33   34   36   41   49   42   45   33         6 rpm rdg   10   12   11   12   4   4   10   10   11   12   11   13   10         3 rpm rdg   8   10   9   10   3   3   8   8   10   11   10   12   8       Plastic   50   78   67   73   73   70   52   57   67   86   71   70   51       viscosity, cp       Yield point,   22   22   21   22   7   10   21   22   23   26   23   20   22       lb/100 ft 2         10-sec gel,   11   12   12   12   4   4   11   11   12   13   12   12   11       lb/100 ft 2         10-min gel,   14   15   15   16   6   9   14   15   14   16   15   15   14       lb/100 ft 2         Electrical   1170   620   640   500   440   480   1170   720   850   500   650   750   1160       stability, volt       HPHT   10.8   11.2   —   —   —   —   10.0   10.6   11.6   10.8   10.2   10.8   10.0       (250° F.), ml       Water in   no   no   —   —   —   —   no   no   no   no   no   no   no       filtrate                    
         [0074]    [0074]                                                                     TABLE 3                       Effect of CHEK-LOSS ® on electrical stability and particle size                                Materials                                                       ISO-TEQ ®,   —   —   0.75   0.75   0.85   0.85   0.95   0.95   1.00   1.00   1.00   1.00       bbl       OMNI-   —   —   12   12   12   12   12   12   12   12   —   —       MUL ®, lb/bbl       Deionized   1.00   1.00   0.25   0.25   0.15   0.15   005   0.05   —   —   —   —       Water, bbl       CHEK-   —   50   —   50   —   50   —   50   —   50   —   50       LOSS ®, lb/bbl       Stirred 30 min       Rolled 16 hr,       150° F.       Properties       Electrical   &lt;5   &lt;5   150   10   230   15   1100   95   2000   2000   2000   2000       stability, volt       Particle Size       Analyses       by Malvern       D (v, 0.1)   —   17.9   —   23.6   —   36.8   —   16.4   —   17.9   —   15.1       D (v, 0.5)   —   64.5   —   84.3   —   95.2   —   70.3   —   60.7   —   65.6       D (v, 0.9)   —   142   —   204   —   203   —   169   —   137   —   175                    
         [0075]    [0075]                                                                                         TABLE 4                       Evaluation of Other fibrous LCM additives as compared to CHEK-LOSS ®                                Materials                                   UNOCAL ECO-   1.0   1.0   1.0   1.0   1.0   1.0   1.0       FLOW       Field Sample (FSR 4341d), bbl       CHEK-LOSS, lb/bbl   —   10   —   —   —   —   —       Slurry Blend*, lb/bbl   —   —   12.5   —   —   —   —       LCM Blend**, lb/bbl   —   —   —   10   —   —   —       KWIK-SEAL Fine,   —   —   —   —   10   —   —       lb/bbl       MASTERSEAL, lb/bbl   —   —   —   —   —   10   —       LCP***, lb/bbl   —   —   —   —   —   —   10       Stirred 30 min       Rolled 16 hr, 150° F.            Properties            Electrical stability, volt   1470   700   740   880   1280   1300   970       600 rpm rdg, 120° F.   126   175   128   166   134   137   150       300 rpm rdg   72   100   70   95   77   77   85       200 rpm rdg   53   78   50   70   58   57   60       100 rpm rdg   32   49   31   42   37   36   37         6 rpm rdg   8   12   8   11   10   10   10         3 rpm rdg   7   10   7   10   8   8   8       Plastic viscosity, cp   54   75   58   71   57   60   65       Yield point, lb/100 ft 2     18   25   12   24   20   17   20       10-sec gel, lb/100 ft 2     10   11   9   13   12   11   12       10-min gel, lb/100 ft 2     13   15   11   15   14   14   14       HPHT (250° F.), cm 3 /30 min   2.0   2.4   —   —   2.4   2.0   —       Water in Filtrate?   no   no   —   —   no   no   —                                                    
         [0076]    [0076]                                                                               TABLE 5                       Performance of KWIK-SEAL Fine compared       to CHEK-LOSS ® Coarse                                Materials:            UNOCAL ECO-FLOW   1.0   1.0   1.0   1.0   1.0       Field Sample       (FSR 4341d), bbl       CHEK-LOSS ® Coarse,   —   10   —   —   —       lb/bbl       CHEK-LOSS ® Coarse   —   —   10   —   —       Retsch ground*,       lb/bbl       KWIK-SEAL Fine,   —   —   —   10   —       lb/bbl       KWIK-SEAL Fine   —   —   —   —   10       Retsch ground*,       lb/bbl       Stirred 30 min       Rolled 16 hr,       150° F.            Properties:            Electrical   1470   900   580   1280   1100       stability, volt       600 rpm rdg,   126   150   160   134   145       120° F.       300 rpm rdg   72   85   90   77   83       200 rpm rdg   53   63   67   58   61       100 rpm rdg   32   38   41   37   37         6 rpm rdg   8   12   12   10   11         3 rpm rdg   7   11   11   8   10       Plastic viscosity,   54   65   70   57   62       cp       Yield point,   18   20   20   20   21       lb/100 ft 2         10-sec gel,   10   12   12   12   12       lb/100 ft 2         10-min gel,   12   14   16   14   14       lb/100 ft 2         Particle Size       Analyses of       Ground LCM additives       by Malvern:       D (v, 0.1)           12.96       15.11       D (v, 0.5)           100.9       99.4       D (v, 0.9)           335.8       369                                    
         [0077]    [0077]                                                                                 TABLE 6                       PPA STUDY - Evaluation of KWIK-SEAL ® Fine       compared to CHEK-LOSS ® Coarse in a laboratory       prepared 12 lb/gal SYN-TEQ ® fluid                                Materials                               Lab-Prepared Base   1.0   1.0   1.0   1.0   1.0   1.0       Mud*, bbl       CHEK-LOSS ®, lb/bbl   —   10   —   —   —   —       CHEK-LOSS ® Coarse,   —       10       lb/bbl       CHEK-LOSS ® Coarse   —   —   —   10   —   —       Retsch ground**,       lb/bbl       KWIK-SEAL ® Fine,   —   —   —   —   10   —       lb/bbl       KWIK-SEAL ® Fine   —   —   —   —   —   10       Retsch ground**,       lb/bbl       Stirred 30 min       Rolled 16 hr,       150° F.            Properties            Electrical   1000   440   600   475   750   700       stability, volt       600 rpm rdg,   113   120   114   118   94   112       120° F.       300 rpm rdg   73   75   76   75   60   70       200 rpm rdg   58   59   60   59   45   53       100 rpm rdg   40   42   43   43   32   36         6 rpm rdg   17   17   17   17   14   15         3 rpm rdg   15   15   15   15   12   13       Plastic   40   45   38   43   34   42       viscosity, cp       Yield point,   33   30   38   32   26   28       lb/100 ft 2         10-sec gel,   17   17   17   17   14   15       lb/100 ft 2         10-min gel,   19   19   19   19   16   18       lb/100 ft 2         PPA (90-micron,       250° F.)       Initial spurt   4.2   3.0   3.0   3.4   2.8   3.2       loss, ml       Total loss, ml   8.2   5.8   6.6   7.0   5.6   4.8                                            
         [0078]    From the foregoing, it was concluded that the intrinsic affinity of cellulosic fibers for water was the cause of the influence of these fibers on electrical stability. Decreased electrical stability values were attributable to swollen, hydrated fibers coming into contact with the electrical stability meter probe. The magnitude of the phenomenon was related to the amount of available water—i.e. the more water, the lower the value. Therefore, the reduction in electrical stability increased as oil/water ratios decreased. Water wetting of solids was never observed in the test fluids. The bar chart of FIG. 1 summarizes the variety of LCM effects upon electrical stability. Particulate LCMs such as MIL-CARB® had no effect. Mud property data is presented in the foregoing Tables, and in FIG. 2.  
         [0079]    The following are oil mud evaluations detailing routine analytical results of submitted field mud samples used in the test matrices.  
                                             TABLE 7                                       Sample:   A           Sample Used For:   Drilling           Mud System:   Syn-Teq           Depth taken, feet:   14800                        External Phase-Oil:   Iso-   S G, Weight Material:   4.2           Teq               Mud Weight, lbm/gal:   17.1   Density of Oil,   6.6               lbm/gal:       Specific Gravity   2.05   Excess Lime, lbm/bbl   1.04       of Mud:       Rheologies @, ° F.:   150   Total Calcium, mg/L   12000               mud       600 rpm:   98   Total Chlorides, mg/L   26000               mud       300 rpm:   58   CaCl2, mg/L mud   40820       200 rpm:   44   CaCl2, lbm/bbl of   14.29               mud       100 rpm:   28   CaCl2, mg/L   402,797         6 rpm:   8   CaCl2, % by weight   31.2         3 rpm:   7   Brine Density, g/ml   1.29       Plastic Viscosity,   40   Corrected Brine, %   10.1       cPs:       by vol.       Yield Point, lbf/   18   Corrected Solids, %   38.9       100 ft 2 :       by vol.       Initial Gel, lbf/   9   Average Solids   3.90       100 ft 2 :       Density,               g/ml       10 min Gel, lbf/   12   Weight Material, %   31.3       100 ft 2 :       by vol.       30 min Gel, lbf/   13   Weight Material,   460.0       100 ft 2 :       lbm/bbl       API, mls/30 mins:       Low Gravity Solids, %   7.6               by vol.       HT-HP Temp, ° F.:   300   Low Gravity Solids,   70.3               lbm/bbl       HT-HP, mls/30 mins:   2.2   Oil:Water Ratio =   15.0               Water       Pom, mls/1 ml mud:   0.8   Oil:Water Ratio =   85.0               Oil       AgN03, mls/1 ml mud:   2.6   Corrected Water   16.6               Ratio       EDTA, mls/1 ml mud:   3   Corrected Oil   83.4               Ratio       ES, volts:   1200       Solids, % by vol.:   40       Water, % by vol.:   9       Oil, % by vol.:   51                  
 
         [0080]    [0080]                                             TABLE 8                                       Sample:   E           Sample Used For:   Drilling           Mud System:   ECOFLOW 200           Depth taken, feet:                        External Phase-Oil:   Eco-   S G, Weight Material:   4.2           flow               Mud Weight, lbm/gal:   16.6   Density of Oil,   6.6               lbm/gal:       Specific Gravity   2.00   Excess Lime, lbm/bbl   3.51       of Mud:       Rheologies @, ° F.:   150   Total Calcium,   11200               mg/L mud       600 rpm:   82   Total Chlorides,   24000               mg/L mud       300 rpm:   47   CaCl2, mg/L mud   37680       200 rpm:   35   CaCl2, lbm/bbl   13.19               of mud       100 rpm:   22   CaCl2, mg/L   530,455         6 rpm:   6   CaCl2, % by weight   38.6         3 rpm:   5   Brine Density, g/ml   1.38       Plastic Viscosity,   35   Corrected Brine, %   7.1       cPs:       by vol.       Yield Point, lbf/   12   Corrected Solids, %   39.9       100 ft 2 :       by vol.       Initial Gel, lbf/   7   Average Solids   3.71       100 ft 2 :       Density, g/ml       10 min Gel, lbf/   11   Weight Material, %   27.2       100 ft 2 :       by vol.       30 min Gel, lbf/   11   Weight Material,   399.4       100 ft 2 :       lbm/bbl       API, mls/30 mins:       Low Gravity Solids, %   12.7               by vol.       HT-HP Temp, ° F.:       Low Gravity Solids,   118.1               lbm/bbl       HT-HP, mls/30 mins:       Oil:Water Ratio =   10.2               Water       Pom, mls/1 ml mud:   2.7   Oil:Water Ratio =   89.8               Oil       AgN03, mls/1 ml   2.4   Corrected Water   11.8       mud:       Ratio       EDTA, mls/1 ml mud:   2.8   Corrected Oil   88.2               Ratio       ES, volts:   1360       Solids, % by vol.:   41       Water, % by vol.:   6       Oil, % by vol.:   53                    
         [0081]    [0081]                                             TABLE 9                                       Sample Number:   E           Sample Used For:   Drilling           Mud System:   Syn-Teq           Depth taken, feet:                        External Phase-Oil:   Eco-   S G, Weight Material:   4.2           Flow 200               Mud Weight, lbm/gal:   17.0   Density of Oil,   6.5               lbm/gal:       Specific Gravity   2.04   Excess Lime,   5.46       of Mud:       lbm/bbl       Rheologies @, ° F.:   150   Total Calcium,   14800               mg/L mud       600 rpm:   89   Total Chlorides,   30000               mg/L mud       300 rpm:   52   CaCl2, mg/L mud   47100       200 rpm:   38   CaCl2, lbm/bbl   16.48               of mud       100 rpm:   25   CaCl2, mg/L   530,455         6 rpm:   7   CaCl2, % by weight   38.6         3 rpm:   6   Brine Density,   1.38               g/ml       Plastic Viscosity,   37   Corrected Brine, %   8.9       cPs:       by vol.       Yield Point, lbf/   15   Corrected Solids, %   38.1       100 ft 2 :       by vol.       Initial Gel, lbf/   8   Average Solids   3.94       100 ft 2 :       Density, g/ml       10 min Gel, lbf/   12   Weight Material, %   31.7       100 ft 2 :       by vol.       30 min Gel, lbf/   13   Weight Material,   466.6       100 ft 2 :       lbm/bbl       API, mls/30 mins:       Low Gravity Solids, %   6.4               by vol.       HT-HP Temp, ° F.:   300   Low Gravity Solids,   59.1               lbm/bbl       HT-HP, mls/30 mins:   2   Oil:Water Ratio =   12.4               Water       Pom, mls/1 ml mud:   4.2   Oil:Water Ratio =   87.6               Oil       AgN03, mls/1 ml mud:   3   Corrected Water   14.3               Ratio       EDTA, mls/1 ml mud:   3.7   Corrected Oil   85.7               Ratio       ES, volts:   1420       Solids, % by vol.:   39.5       Water, % by vol.:   7.5       Oil, % by vol.:   53                    
       EXAMPLE 2  
       [0082]    The following LCM&#39;s were obtained from Grinding &amp; Sizing Co. labeled as: “Wood Fiber” (pine), “Grape Pumice”, “Pith”, “Furfural” and “Total Control” (ground rubber). Ground coconut shell was obtained from Reade Co. in 325 mesh size and 80-325 mesh size ( “Reade 325F” and “Reade 325/80,” respectively).  
         [0083]    Equipment  
         [0084]    1. Prince Castle mixer  
         [0085]    2. Fann viscometer, Model 35A  
         [0086]    3. Thermometer, dial, 0-220° F.  
         [0087]    4. Balance with precision of 0.01 g  
         [0088]    5. Sieves (conforming to ASTM E11 requirements)  
         [0089]    6. Roller oven, 150-250±5° F. (66-121±3° C.)  
         [0090]    7. Spatula  
         [0091]    8. Timer: interval, mechanical or electrical, precision of 0.1 minute  
         [0092]    9. Jars (approximately 500 ml capacity) with sealing lids  
         [0093]    10. Heating cup, OFI, 115 volt  
         [0094]    11. Particle Plugging Apparatus  
         [0095]    12. Aloxite disks  
         [0096]    13. Malvern Mastersizer  
         [0097]    PROCEDURES  
         [0098]    The following INTEQ Fluids Laboratory procedures were used  
         [0099]    Recommended Practice Standard Procedure for Field Testing Oil-Based Drilling Fluids, API Recommended Practice 13B-2, Third Edition, February 1998  
         [0100]    Recommended Practice Standard Procedure for Field Testing Water-Based Drilling Fluids, API Recommended Practice 13B-1, Second Edition, September 1997  
         [0101]    Instrumentation Manual for Malvern Mastersizer  
         [0102]    The following results were observed:  
                                                 TABLE 10                       Evaluation of Various Fibrous LCM Additives from Grinding       &amp; Sizing Co., Inc., as compared to CHEK-LOSS                                Materials:                                   Field Mud FSR No. 4502, bbl   1.0   1.0   1.0   1.0   1.0   1.0   1.0       CHEK-LOSS, lb   —   10   —   —   —   —   —       Wood Fiber, lb   —   —   10   —   —   —   —       Grape Pumice, lb   —   —   —   10   —   —   —       Pith, lb   —   —   —   —   10   —   —       Furfural, lb   —   —   —   —   —   10   —       Total Control, lb   —   —   —   —   —   —   10       Stirred 15 min; rolled 16 hr, 150° F.       Properties:       600 rpm rdg at 120° F.   91   119   114   100   108   108   107       300 rpm rdg   52   69   66   60   64   64   63       200 rpm rdg   38   51   48   44   47   47   46       100 rpm rdg   24   31   30   28   30   30   28         6 rpm rdg   7   8   8   8   8   8   8         3 rpm rdg   5   6   6   6   6   6   6       Plastic viscosity, cp   39   50   48   40   44   44   44       Yield point, lb/100 sq ft   13   19   18   20   20   20   19       10-sec gel, lb/100 sq ft   8   9   9   9   9   9   9       10-min gel, lb/100 sq ft   11   12   12   12   12   12   12       Electrical stability, volt   750   300   350   670   540   490   590       Pom, mls/1 ml mud   1.6   1.55   —   1.55   —   —   —       Particle plugging apparatus results,       (300° F., 1000 psi, 90-micron)       Spurt loss, ml   3.0   4.8   —   2.0   —   —   —       Final total loss, ml   5.0   7.2   —   2.8   —   —   —                  
 
         [0103]    Oil-Mud Sample Evaluation Report (FSR No. 4502)  
                                               External Phase-   Eco-   S G, Weight Material:   4.2       Oil:   flow               Mud Weight,   15.3   Density of Oil, lbm/gal:   6.6       lbm/gal:       Specific Gravity   1.84   Excess Lime, lbm/bbl   1.95       of Mud:       Rheological   150   Total Calcium, mg/L mud   10400       Properties, ° F.:       600 rpm:   60   Total Chlorides,   22000               mg/L mud       300 rpm:   35   CaCl2, mg/L mud   34540       200 rpm:   26   CaCl2, lbm/bbl of mud   12.09       100 rpm:   17   CaCl2, mg/L   347,539         6 rpm:   5   CaCl2, % by weight   27.7         3 rpm:   4   Brine Density, g/ml   1.25       Plastic   25   Corrected Brine, %   9.9       Viscosity,       by vol.       cPs:       Yield Point,   10   Corrected Solids, %   35.1       lbf/100 ft 2 :       by vol.       Initial Gel,   7   Average Solids   3.65       lbf/100 ft 2 :       Density, g/ml       10 min Gel,   10   Weight Material, %   22.6       lbf/100 ft 2 :       by vol.       30 min Gel,   10   Weight Material,   331.5       lbf/100 ft 2 :       lbm/bbl       API, mls/30 mins:       Low Gravity Solids, %   12.5               by vol.       HT-HP Temp, ° F.:       Low Gravity Solids,   116.0               lbm/bbl       HT-HP, mls/30       Oil:Water Ratio =   14.1       mins:       Water       Pom, mls/1   1.5   Oil:Water Ratio =   85.9       ml mud:       Oil       AgN03, mls/1   2.2   Corrected Water Ratio   15.3       ml mud:       EDTA, mls/1   2.6   Corrected Oil Ratio   84.7       ml mud:       ES, volts:   700       Solids, % by   36       vol.:       Water, % by vol.:   9       Oil, % by vol.:   55                  
 
         [0104]    [0104]                                                                               TABLE 11                       Evaluation of Grinding &amp; Sizing Co. Grape Pumice, as compared       to CHEK-LOSS, in a Solids-Laden Oil-Based Field Mud                                    Materials:                Field Mud (FSR No. 4522), bbl   1.0   1.0   1.0           CHEK-LOSS, lb   —   10   —           Grape Pumice, lb   —   —   10           Stirred 15 min; rolled 16 hr, 150° F.                Properties:                600 rpm rdg at 120° F.   150   190   150           300 rpm rdg   81   104   80           200 rpm rdg   58   72   56           100 rpm rdg   32   42   31             6 rpm rdg   5   7   5             3 rpm rdg   4   5   4           Plastic viscosity, cp   69   86   70           Yield point, lb/100 sq ft   12   18   10           10-sec gel, lb/100 sq ft   7   8   7           10-min gel, lb/100 sq ft   23   27   24           Electrical stability, volt   620   350   585           Pom, mls/1 ml mud   1.0   1.0   1.0           Particle plugging apparatus results,           (300° F., 1000 psi, 90-micron)           Spurt loss, ml   4.6   5.2   2.8           Final total loss, ml   9.0   9.6   5.2                        
         [0105]    [0105]                                                                       TABLE 12                       Evaluation of Reade Co. Ground Coconut Shell, as compared       to CHEK-LOSS, in a Solids-Laden Oil-Based Field Mud                                Materials:            Field Mud (FSR No. 4522), bbl   1.0   1.0   1.0   1.0       CHEK-LOSS, lb   —   10   —   —       Reade 325F, lb   —   —   10   —       Reade 80/325, lb   —   —   —   10       Stirred 15 min; rolled 16 hr, 150° F.            Properties:            600 rpm rdg at 120° F.   150   190   173   185       300 rpm rdg   81   104   97   102       200 rpm rdg   58   72   72   75       100 rpm rdg   32   42   41   42         6 rpm rdg   5   7   8   6         3 rpm rdg   4   5   6   4       Plastic viscosity, cp   69   86   76   83       Yield point, lb/100 sq ft   12   18   21   19       10-sec gel, lb/100 sq ft   7   8   11   11       10-min gel, lb/100 sq ft   23   27   48   40       Electrical stability, volt   620   350   605   585       Pom, mls/1 ml mud   1.0   1.0   —   0.95       Particle plugging apparatus results,       (300° F., 1000 psi, 90-micron)       Spurt loss, ml   4.6   5.2   —   3.4       Final total loss, ml   9.0   9.6   —   6.6                    
         [0106]    The coconut materials had very minimal impact upon the electrical stability value of the base fluid. However, these materials appeared to be kilned, thus making them more characteristic as a particulate rather than a fiber. Resultant rheological properties were not satisfactory.  
         [0107]    In Data Tables 11 and 12, Formula 4522 was the following:  
         [0108]    Oil-Mud Sample Evaluation Report (FSR No. 4522)  
                                               External Phase-Oil:   Diesel   S G, Weight Material:   4.2       Mud Weight, lbm/gal:   16.5   Density of Oil, lbm/gal:   7.1       Specific Gravity of Mud:     1.98   Excess Lime, lbm/bbl   1.30       Rheological Properties, ° F.:     150, 120   Total Calcium, mg/L mud   5200       600 rpm:     96, 137   Total Chlorides, mg/L mud   9000       300 rpm:     52, 75   CaCl2, mg/L mud   14130       200 rpm:     36, 52   CaCl2, lbm/bbl of mud   4.95       100 rpm:     21, 29   CaCl2, mg/L   150,804         6 rpm:     4, 5   CaCl2, % by weight   13.6         3 rpm:     3, 4   Brine Density, g/ml   1.11       Plastic Viscosity, cPs:     44, 62   Corrected Brine, % by vol.   9.4       Yield Point, lbf/100 ft 2 :     8, 13   Corrected Solids, % by vol.   39.1       Initial Gel, lbf/100 ft 2 :     5, 6   Average Solids Density, g/ml   3.67       10 min Gel, lbf/100 ft 2 :     21, 22   Weight Material, % by vol.   25.7       30 min Gel, lbf/100 ft 2 :     29, 30   Weight Material, lbm/bbl   377.4       API, mls/30 mins:       Low Gravity Solids, % by vol.   13.5       HT-HP Temp, ° F.:   300      Low Gravity Solids, lbm/bbl   124.8       HT-HP, mls/30 mins:    9.2   Oil:Water Ratio = Water   14.9       Pom, mls/1 ml mud:   1    Oil:Water Ratio = Oil   85.1       AgN03, mls/1 ml mud:    0.9   Corrected Water Ratio   15.4       EDTA, mls/1 ml mud:    1.3   Corrected Oil Ratio   84.6       ES, volts:   650          Solids, % by vol.:   39.5       Water, % by vol.:   9        Oil, % by vol.:   51.5                  
 
         [0109]    [0109]                                                                               TABLE 13                       Evaluation of Grinding &amp; Sizing Co. Grape Pumice, as compared       to CHEK-LOSS, in a Laboratory-Prepared Water-Based Mud                                    Materials:                Lab-Prepared Mud (FSR No.   1.0   1.0   1.0           4423b), bbl           CHEK-LOSS, lb   —   10   —           Grape Pumice, lb   —   —   10           Stirred 15 min; rolled 16 hr, 150° F.                Properties:                600 rpm rdg at 120° F.   74   141   90           300 rpm rdg   40   80   52           200 rpm rdg   28   57   40           100 rpm rdg   17   35   25             6 rpm rdg   3   9   8             3 rpm rdg   2   7   6           Plastic viscosity, cp   24   61   38           Yield point, lb/100 sq ft   16   19   14           10-sec gel, lb/100 sq ft   6   14   14           10-min gel, lb/100 sq ft   23   38   44           pH   9.0   8.4   7.5           API filtrate, ml   0.6   0.4   0.4                        
         [0110]    In Data Table 13, Formulation 4423b was the following:  
                                                             Formulation (FSR 4423b)                                        Water, bbl   0.6           MILGEL, lb   4.0           Soda Ash, lb   1.0           NEW-DRILL LV, lb   0.5           Sea salt, lb   8.8           MIL-PAC LV, lb   1.0           CHEMTROL X, lb   6.0           LIGCO, lb   6.0           TEQ-THIN, lb   3.0           SULFATROL, lb   2.0           Caustic Soda, lb   2.5           AQUA-MAGIC, % vol   3.0           ALL-TEMP, lb   1.0           Rev Dust, lb   18.0           MIL-BAR, lb   450.0           MIL-CARB, lb   10.0           CHECK-LOSS, lb   3.0                      
 
         [0111]    Grape Pumice appears to fulfill the needed characteristic of being composed of more lignin rather than cellulose. Grape Pumice caused significantly less impact (5-10% decreases) upon electrical stability values, as compared to 50-60% decreases when adding CHEK-LOSS. Grape Pumice also induced less impact upon the plastic viscosities of the oil muds, as compared to CHEK-LOSS. Grape Pumice provided better PPA (particle plugging apparatus) results, as compared to CHEK-LOSS at test conditions of 300° F., 1000 psi differential, 90-micron aloxite disk.  
       EXAMPLE 3  
       [0112]    The papermaking industry uses a measurement called the Water Retention Value (WRV), which gives the amount of water intimately associated with a given dry weight of wood pulp. This represents the capacity of fibers to swell in the presence of water. This value varies with the source of plant fibers (corn, peanut, walnut, almond, coconut, etc.). The paper industry wants more cellulose, less lignin. The need in this application is to choose a plant fiber source with a ratio of more lignin with less cellulose. Lignin, which serves as the “skeletal” structure for plants, is significantly less water-absorbent.  
         [0113]    The following described procedure is a modification of the TAPPI 1991 UM-256 procedure used in the papermaking industry. Equipment used included:  
         [0114]    1. Prince Castle mixer  
         [0115]    2. Tachometer  
         [0116]    3. 500-ml glass jars with lids  
         [0117]    4. Deionized water  
         [0118]    5. Electronic balance  
         [0119]    6. Vacuum pump  
         [0120]    7. 2-liter Erlenmeyer flask  
         [0121]    8. Buchner funnel  
         [0122]    9. Whatman filter paper No. 41  
         [0123]    An amount of 25 g test material was added to a glass jar. 250 ml of deionized water was then added. The slurry was sheared at 3000 rpm for 5 min. The glass jar was capped and rolled 16 hr at 150° F. After cooling, the jar contents was poured into an assembled Buchner funnel (using Whatman filter paper No. 41) fitted on a 2-liter Erlenmeyer flask, hooked to a vacuum pump. Filtration was conducted for two hours maximum. The Buchner funnel with test material content was removed from the flask and was weighed. Calculation of the WRV would be as follows:  
         [0124]    (Buchner funnel with filter paper and retained wet test material minus Buchner funnel with wet paper) minus initial 25 g dry test material. Resultant value then divided by initial 25 g dry test material.  
         [0125]    Results were, as follows:  
                                                                   Weight of                   Weight,   filtered, wet           Test Material   g   Material, g   WRV                           Buchner funnel with wet   602.2   —   —           paper           Above with MIL-CARB   630.8   28.6   0.144           Above with Grape Pumice   633.6   31.4   0.256           Above with CHEK-LOSS   727.8   125.6   4.024           Above with Mud-Liner   745.0   142.8   4.712           Above with Liquid Casing   715.0   112.8   3.512                      
 
         [0126]    The Grape Pumice material appears to fulfill the needed characteristic of being composed of more lignin rather than cellulose.  
         [0127]    Particle size analyses by Malvern Mastersizer instrumentation showed the Grape Pumice to be near-similar to CHEK-LOSS:  
                                                           Test Material   D (v, 0.1)   D (v, 0.5)   D (v, 0.9)                           Grape Pumice   16 μm   69 μm   166 μm           CHEK-LOSS   21 μm   68 μm   185 μm                      
 
         [0128]    As evident by this data, particle size distribution would not contribute to differentiating WRV between the two materials; Grape Pumice exhibits significantly less water absorbency, a characteristic favorable for application as a LCM in invert emulsion drilling fluids while not interfering with emulsion stability measurements.  
       EXAMPLE 4  
       [0129]    The Grape Pumice material, being acidic, will lower pH levels in aqueous muds. A test was conducted by adding 10 lb Grape Pumice to a 1-bbl equivalent of deionized water. Resultant pH was 3.5. Blending 10 lb Grape Pumice with 0.2 lb soda ash kept the pH at 7.0.  
         [0130]    Because of this concern, alkalinity levels were measured in the oil muds tested with Grape Pumice. There were no changes, thus the Grape Pumice seems to be preferentially oil-wetted.  
         [0131]    Persons of ordinary skill in the art will recognize that many modifications may be made to the present invention without departing from the spirit and scope of the invention. The embodiment described herein is meant to be illustrative only and should not be taken as limiting the invention, which is defined in the claims.