METHOD FOR DETERMINING BOREHOLE OR CAVITY CONFIGURATION THROUGH INERT GAS INTERFACE

Abstract: A method of determining the erosion of a borehole or cavity (10) by providing a source of liquid inert gas, preferably nitrogen, placing the inert gas in a storage tank (20), and suspending the storage tank so that one may determine the actual weight of the nitrogen as it is withdrawn from the tank in liquid state. There is further provided hydraulic means (36, 38) for lifting or lowering the storage tanks suspended from a weight cell (50) as a tank is place into use or non-use. Further, the liquid nitrogen is pumped from the storage tank with the use of a reciprocating pump (56), and converted into gaseous nitrogen (in the state of 100<o>F,) and is injected into a borehole (10) or the like. The nitrogen gas is then allowed to flow under a certain pressure down the borehole, and due to the properties of nitrogen gas, the nitrogen interfaces at a horizontal plane (58) as it moves down the borehole.

Description: METHOD FOR DETERMINING BOREHOLE OR CAVITY CONFIGURATION THROUGH INERT GAS INTERFACE > BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the measurement of bore¬ holes and underground caverns. In particular, this invention relates to the configuration of a borehole at certain depth intervals with the use of an inert gas, such as nitrogen interfaced by determining the change in the weight of the gas from its source. 2. General Background. In the oil and gas industry, and in other related industries where there are storage caverns and the like within the earth for storing minerals such as oil, natural gas, sulphur, etc., these caverns, often being at a great depth beneath the surface of the earth, are reached through the use of boring a borehole from the surface of the earth down into the cavern. The bore ¬ hole, of course, would accommodate the flow of minerals that are^o be stored in the storage cavern both down ¬ ward, and the movement of the minerals up through the borehole as the minerals are utilized. After a certain depth, these boreholes are simply holes drilled within the earth and have no pipe or casing to support the walls which may serve to prevent erosion or the like of the walls of the borehole. That being the case, in the preparation of the cavern by inserting salt water, or in the insertion.of or the retrieval of the liquid minerals that are flowing through the borehole, the OIvi walls of the borehole become eroded, and the borehole itself may be in such a state that it is no longer effective in being used as a conduit for the passage of minerals and the like into the cavern. Therefore, it is essential in the storage of such minerals and the preparation of the cavern, that the boreholes are carefully monitored in order to determine whether or not the borehole is in the proper shape that it is not so eroded that it is ineffective in its use. Likewise, often the configuration of the cavern itself is measured in order to determine the extent of erosion of the cavern. One known process for measuring the configuration of the borehole is to use an inert gas such as nitrogen gas and insert it down the hole. The pressure of the gas is measured as it leaves its source, and a measurement is attempted in order to determine how much gas is being used to fill a certain void within the borehole. What is utilized in the present state of the art is a measur¬ ing device which is marketed under the trademark of a "Barton Guage" which records the number of inches of nitrogen being pumped out of the tank. This particular method falls very short of being in the least bit accu¬ rate, and is totally ineffective. At present, both governmental and industry requirements are such that the amount of inert gas being used to measure the configura- tion of the borehole must be within five pounds of the actual amount being pumped down the hole, and under the present method, this determination is ineffective. There have been several patents which speak to the measurement of pressure, etc. either down the borehole or methods of determining the size of an orifice, the most pertinent being as follows: U. S. Patent No. 2,374,154 issued to C. B. Moore entitled "Comparator Gauge" teaches the use of a type of pneumatic guage for recording demensions of an internal bore at successive locations down the borehole. Essen¬ tially, the apparatus includes a transmitter head with a pressure transmitter within on the end of a flexible tube which is able to extend the length of the bore to be measured. It further provides an , air compressor which supplies pressurized fluid to a receiver through the supply pipe to pressure regulators. The fluid sup¬ plied to the transmitter head is then delivered through the bore to the fluid pressure chamber. The apparatus then provides a readout of the pressurization within the bore which is then transmitted onto a chart as the transmitter is moved down periodically the borehole. This apparatus in no way measures the configuration of the borehole due to the change in the weight of the measuring medium such as in this case, nitrogen. U. S. Patent No. 2,513,374 issued to C. Stead, et al entitled "Measuring Apparatus for Gauge Determination of J7Ξ S:"£ST Dimensions of Bodies with Flow of Fluid under Pressure From an Orifice" teaches the use of a measuring appara¬ tus which has the capability of gauging dimensions of bodies by comparison with those of a master or standard, and determining the deviation from the "standard." The apparatus uses a Venturi means for providing differen¬ tial fluid pressure for efficient operation of a gauge meter such as air and to permit bi-manual manipulation adjustment of a valve to 0 for comparatively measuring the dimensions of the body. In the claims of this par¬ ticular patent, there is claimed a Venturi means as part of the combination for responding to the differential pressures and verifying the dimensions of the orifice being engaged. U. S. Patent No. 1,919,546 issued to H. W. Fletcher entitled "Method and Apparatus for Testing Internal Diameter of Tubes" teaches the use of a device for test¬ ing the uniformity of the internal diameter of tubes so that inequalities within the internal walls of the tubes may be found. The invention is carried out by noting the amount of fluid that leaks past a cylinder of uni ¬ form diameter that moves within the tube. This is quite unlike the invention which rel s on the interfacting of the layer of nitrogen with the atmosphere as it moves down the hole and conforms itself to the irregularities within the borehole. Please note also in the claims that there is claimed a gauge piston form to fit the tube loosely, and the other mechanisms which relate to this type of measurement. ϋ. S. Patent No. 2,669,864 issued to 0. C. Brewster entitled "Pneumatic Bore Gauge" is basically an improve¬ ment patent upon pneumatic bore gauges of that time by having the ability to use a bore head to obtain the results of a two-range diameter of the hole. As with the other patent, what is required in this patent is an apparatus having a head which goes down the bore hole for determining the shape of the hole. And there appears to be no language in the patent which does teach the use of this particular apparatus down an oil well bore and is simply a patent on an improved bore head. U. S. Patent No. 4,000,655 issued to Jones entitled "Measuring Devices for Bores and Ducts" teaches the use of a means for measuring the irregularities on the inner surface of a pipeline by having a fluid filled envelope whereby the surface of the envelope would fill the irregularities of the hole. There would be a means for sensing the pressure variations within the envelope. U. S. Patent No. 3,456,504 issued to C. C. Bombardieri entitled "Sampling Method" teaches the use of a method for analyzing a subsurface formation by introducing two types of fluid at a selected ratio and analyzing the fluid following their injections into the formation. SUBSTITUTE SHEET the mud system or the rate of change in the mud volume for detecting the abnormal conditions when the rate of makeup mud addition differs from the rate of solids removed from down the hole. 3. General Discussion of the Present Invention The preferred embodiment of the method and apparatus of the present invention solves the problems encountered in the present state of the art in a simple and straightforward manner. What is provided in the present invention is a method for determining the erosion of a borehole or cavity by providing a source of liquid inert gaβ, preferably nitrogen, placing the inert gas in a storage tank, and suspending the storage tank so that one may determine the actual weight of the nitrogen as it is withdrawn from the tank in liquid state. There is further provided hydraulic means for lifting or lowering the storage tanks suspended from a weight cell as a tank iβ placed into use or non-use. Further, the liquid nitrogen is pumped from the storage tank with the use of a reciprocating pump, and converted into gaseous nitro¬ gen (in the state of 100 * F,) and is injected into a borehole or the like. The nitrogen gas is then allowed to flow under a certain pressure down the borehole, and due to the properties of nitrogen gas, the nitrogen interfaces at a horizontal plane as it moves down the borehole. There is further provided a wire line means for measuring the movement of the nitrogen down the borehole, and the wire line enables to determine the SUSCTJTUTE SHEET position of the interface at predetermined intervals, preferably one foot intervals down the hole. There is further provided a digital readout means, which electrically records the change in weight of the nitro¬ gen tank as the nitrogen is pumped down the hole. Upon the nitrogen reaching one-foot intervals, the weight of the nitrogen is recorded from the digital readout, and is manually plotted as the nitrogen moves down the bore¬ hole. Therefore, knowing the amount of weight of nitro¬ gen utilized in a particular interval, i.e. one foot, and the temperature of the nitrogen, and the pressure of the nitrogen in the hole, one can determine the area that that nitrogen is occupying in the hole. That being the case, when erosion has occurred within a particular one-foot area, a greater amount of nitrogen would be utilized, and therefore, one has a reading onto the extent of the erosion within the hole at that particular interval. There may be further provided computer means for receiving the information from the digital readout and the temperature weight and pressure of the nitrogen, and providing a graphic readout of the shape of the borehole as the nitrogen moves down the borehole and interfaces therein. Therefore, it is an object of the present invention to provide a method for determining the errosion within a cavern or borehole. It is a further object of the present invention to provide a method for accurately determining the shape of a borehole through the calculating of predetermined SUBSTITUTE SHEET qualities of an inert gas as it moves between predeter¬ mined intervals down the borehole. It is still a further object of the present inven¬ tion to provide a system whereby a change in weight of an inert gas stored in a tank enables one to calculate the erosion that has occurred within an underground cavity. It is yet a further object of the present invention to provide an apparatus for storing liquid inert gas, weighing the inert gas, moving the inert gas from stor¬ age to the cavern to be measured, and providing a read¬ out means for determining the change in the weight of the inert gas as it moves down the borehole. It is still a further object of the present inven¬ tion to provide a method for determining the shape of a borehole by providing an inert gas under a given pres¬ sure, temperature, and flow rate, and determining the weight of the inert gas at certain intervals down the bore hole, and further calculating and graphing the shape of the borehole from these factors. In order to accomplish the above stated objects of the present invention, it is a feature of the present invention to provide an inert gas such as nitrogen for pumping down a borehole in order to measure the shape of the borehole. It is an additional feature of the present invention to provide a means for storing the nitrogen in the SUBSTITUTE Sh'^ T liquid form and providing an apparatus for accurately weighing the nitrogen to provide a given weight of the nitrogen prior to extraction from the storage tank. It is yet a further feature of the present invention to provide a digital readout means for monitoring the change in the weight of nitrogen as it is pumped down the borehole. It is still a further feature of the present inven¬ tion to provide a pumping means to pump the liquid nitrogen from the storage tank into the borehole as gaseous nitrogen. It is still a further feature of the present inven¬ tion to provide a wire line means in order to determine the depth of the movement of the interface of the nitro¬ gen down the borehole at predetermined intervals. 4. Brief Description of the Drawings For a further understanding of the nature and objects of the present invention, reference should be had to the following detailed description, taken in con¬ junction with the accompanying drawings, in which like parts are given like reference numbers and, wherein: Figure 1 is an overall view of the preferred embodi¬ ment of the apparatus utilized in the preferred embodi¬ ment of the method of the present invention. 5. Detailed Description of the Preferred Embodiment Figure 1 best illustrates the preferred embodiment of the apparatus utilized in the method of the present invention. There is illustrated in Figure 1 borehole S UBSTITUTE SHEET and/or cavern 10 which is the subject matter to be mea* sured under the present method. As is illustrated, borehole 10 would have its starting point at ground level 12 and would in most cases for a reasonable dis¬ tance down as indicated by numeral 13 be a straight sided borehole, having remained intact for a certain distance down the hole. However, as further illus¬ trated, there is a possibility, and often it is the case, that the straight walls as indicated by numeral 13, the borehole would become eroded due to the passage of minerals, salt water or the like up and down and up the borehole, with erosion areas 14 and 15 being illus¬ trated in order to show the extent of erosion that may occur down the borehole. As was stated earlier, it is imperative that in the safe use of these boreholes in order to fill the storage cavern 16, that the extent of the erosion 14 and 15 be determined accurrately. The result of this determination may result in the drilling of an additional borehole due to the fact that the pre¬ sent borehole is non-usable. The preferred embodiment of the apparatus and the method utilized in the present invention is illustrated in order to accomplish this result of accurracy in mea¬ surement of erosion. There is provided storage tank 20 which is a special tank, known in the art, which can withstand cryogenic temperatures and pressures for the storage of various types of fluid. In this particular case, tank 20 would be filled with liquid nitrogen gas in the preferred embodiment, and storage tank 20 would be placed within framework 22 so that tank 20 is secure¬ ly mounted for further use in the process. .✓^JRE TITUTE SHEET X PO After being filled, the tank 20 and framework 22 is set within weighing frame 24 which comprises a pair of vertically disposed stabilizing beams 26 and 28 placed on either end of the tank, and held into position with horizontally disposed beam 30 which is secured to the upper most ends of beams 28 and 26, thus providing a hanging frame for tank 20 and framework 22. The entire frame and tank containing nitrogen gas is then weighed and the beginning weight is thus determined before the measurement begins. As is seen in the drawing, the upper half of beams 26 and 28 are slideably movable so that the framework is able to adjust up and downward as will be further illustrated. There is further provided extender wire 32 and 34 which are connected at the four corners of the framework 22, and are connected at a single point midway along beam 30, to provide a means for suspending tank 20 and frame 22 from horizontal beam 30 during the process. In order to provide upward and downward movement of suspended tank and frame 22, from horizontal beam 30, there is further provided a pair of hydraulic cylinder 36 and 38 which, are typical hydraulic cylinders, with the hydraulic arms 39 and 40 having upward and downward movement from the pressure of the hydraulic fluid within cylinders 36 and 38. The upper ends of the hydraulic arms 39 and 40 are intergrally attached to the end por tions of horizontal beam 30, so that the upward and downward movements of arms 39 and 40 imparts upward and SUBSTITUTE SHEET downward movement to horizontal beam 30 as indicated by arrows 41. Hydraulic cylinders 36 and 38 are manually controlled by hydraulic power unit 42 which provides hydraulic fluid through lines 43 and 44 to hydraulic cylinder and provide upward and downward movement as the case may be. At that point of connection between extended lines 32 and 34 to horizontal beam 30, there is provided a weight cell 50 which, when the tank 20 and frame 22 is suspended from beam 30, the weight cell indicates the total weight of the unit being suspended from the framework. This total weight is received by electrical digital readout means 52 via electrical line 53, and readout means 52 digitally reads out the total weight of the suspended unit, and will read out any change in the weight as the weight is decreased or increased during the process. In the actual process, once the tank 20 and frame¬ work 22 has been suspended from beam 30, and a digital readout of the total weight from readout means 52 is determined, the liquid nitrogen, which is pressurized within tank 20 is released through line 54, and through the use of reciprocating pump 56, the liquid nitrogen is converted into gaseous nitrogen, preferably under 80* to 100 * , and at a predetermined pressure, the gaseous nitrogen is then transported into borehole 10, via line 54. SUBSTITUTE SHEET The gaseous nitrogen at that temperature, once entering borehole 10 will move down the borehole 10 with a very concise horizontal interface at point 58, so that as more nitrogen gas is pumped, the interface 58 con¬ tinues to move down borehole 10. In order to accurately monitor the position of the interface as it moves down borehole 10, there is provided wire line 60 which is a conventional wire line and has a means 61 for recording the position of interface 58 at given intervals within bore hole 10. In the preferred embodiment of the pre¬ sent invention, the position of interface 58 down bore¬ hole 10 is measured (at one foot or more intervals), and these intervals would be determined by the use of wire line means 61. An operator, who is monitoring the movement of wire line 60 down the borehole, informs a statistician the position of wire line 60 at each interval, at which point the statistician records the digital readout of the weight of the nitrogen unit, which would be a reduced weight as more nitrogen gas is being pumped into the borehole. Of course, when the interface reaches an erosion point such as point 62, since there is a greater width to borehole 10, at this point, a greater loss weight of nitrogen would be recorded at this interval than would have been at earlier intervals when borehole 10 was in the normal configuration. That being the case, the statistician would record this greater weight loss as he would continually down the movement of interface 58 down borehole 10, until nitrogen interface 58 has reached the point that the test is completed. SUBSTITUTE SHEET Following the recording of the various weight changes down the borehole during the test, given the known pressure of the nitrogen gas, the temperature of the gas, and the weight change in the gas, one is able to calculate the area that that gas is occupying, and thus able to plot the configuration of the walls of the bore hole. There may be further provided computer means wherein the information of the gas pressure, temperature, and weight is entered into the computer, and the computer would calculate the area involved, and graphically rep¬ resent the shape of the borehole on a screen or the like as provided by the computer. (Of course, if some turbine-type differential flow meter were to be perfected which would have the capacity to measure the flow of an inert gas, such as nitrogen, down a borehole, and would be able to maintain itself within the required degree of accuracy as is required in the industry, one would be able to accurately measure the flow of the gas, without having to depend on the actual total weight of the liquid nitrogen that is loss from the tank in order to plot the configuration of the borehole and/or the crown of the cavern 16 during the measuring process.) As ancillary use, following the completion of the test, often times the nitrogen gas is maintained within the borehole on the pressure, and from the change in the pressure of nitrogen gas over an extended period of time, one may determine the amount of leakage that is SUBSTITUTE SHEET . - occurring within the borehole, and thus because of leaks which have developed down the borehole, the bore hole, other than the erosion factor, may be unusable if in fact there is great deal of leakage occurring from the walls or the outer most top portion of the borehole. There is provided for further edification a chart which represents the use of the nitrogen down the bore¬ hole, and the results of those tests as the nitrogen moves down the borehole. SCALE: LBS. LBS.N2 USED INJECTED IN INTERFACE NITROGEN PER INTERVAL WELL S.C.F.N2 WELL DEPTH 10,036 44 607.2 1780 9,992 44 607.2 1780 9,870 122 1683.6 1840 9,780 90 1242 1860 9,690 90 1242 1880 9,606 84 1159.2 1900 As illustrated in the above graph, as examples of the method utilized in the present invention, if the starting weight of the liquid nitrogen is shown as 10,036 pounds in column 1, a total of 44 pounds would occupy a twenty foot interval in the borehole, injected at 607.2 S.C.F. at a depth of 1780 feet. Moving down the column, at a depth of 1900 feet the amount of nitro¬ gen necessary to occupy the same twenty foot interval is measured at 84 pounds injected at 1159.2 S.C.F. The Si i ι >nw<r>"r i j .— _ *« »— . —:. ■ OMPI t Λ results of this differential in the two examples illus¬ trate that in the latter case, the borehole or cavity has eroded to an area whereby substantially twice the amount of gaseous nitrogen is required to occupy that same twenty foot interval. As this measurement is taken at consecutive predetermined intervals to a predeter¬ mined depth, one then is able to plot, either manually or with the aid of a computer the visual configuration of the borehole or cavity throughout the entire depth. Because many varying and different embodiments may be made within the scope of the inventive concept taught, and because many modifications may be made in the embodiments herein detailed in accordance with the descriptive requirement of the law, it is to be under¬ stood that the details herein are to be interpreted as illustrative and not in a limiting sense. SUBSTITUTE G::" T

Claims: Claims 1. A method of determining the shape of a borehole or cavity, which comprises the following steps: a. providing a relatively inert fluid; b. measuring the total weight of said fluid? c. delivering said fluid under a known pressure and temperature down the borehole or cavity to be measured; d. monitoring the weight loss of said measured fluid between certain measured intervals within said cavity; e. calculating the area occupied by said fluid within at least one of said intervals. 2. The method in Claim 1, further comprising the step of calculating said area occupied by said fluid at a series of consecutive fluid intervals. 3. The method in Claim 2, further comprising the step of graphically plotting the areas of consecutive intervals to illustrate the shape of said borehole and cavity measured. 4. The method in Claim 1, wherein said fluid is gaseous nitrogen or some other relatively inert gas. 5. The method in Claim 1, wherein said fluid is contained in a tank or the like under known pressure. 6. The method in Claim 1, wherein said fluid is suspended in said tank for determining the weight of said fluid within said tank at the onset. SUBSTITUTE SHEET - IS - 7. The method in Claim 1, further providing digital readout means for providing the change in weight of said fluid during said process. 8. T he method in Claim 1, further providing the step of entering into a computer the known temperature, pressure and weight of said fluid within said given intervals, said computer graphically plotting the shape of said cavity. 9. The method in Claim 1, further comprising means to calculate the movement of said fluid down said bore hole, said means comprising a wire line movable down said cavity and recording distance traveled. 10. The method in Claim 1, further comprising pump means for transporting said fluid from said storage tank under pressure, wherein during said transport of said fluid is converted from a liquid to a gaseous state. 11. A method of determining the shape of a borehole or cavity which comprises the following steps: a. providing a relatively inert fluid containerized and under pressure, said fluid preferably being liquid nitrogen; b. calculating the total weight of said fluid in said container; c. providing digital readout means for recording the total weight of said fluid within said container; d. transporting said fluid from said container into the borehole or cavity to be measured, said fluid trans¬ ported at a known pressure and t e_ιrκξτ r»r* ,, τ e. providing means movable upward and downward within said cavity or borehole to record linear movement of said fluid interfaced within said borehole or cavity; f. recording the change in total weight of said pressurized fluid, said weight change being equal to the amount of fluid delivered down said bore hole or cavity between two predetermined points within said cavity; g. plotting the area of fluid occupied within given intervals down said cavity to receive a reading of the configuration of said cavity based upon weight of fluid within said hole between said given intervals. 12. The method in Claim 11, further providing pump means for transporting said fluid from said container to said borehole. 13. The method in Claim 11, wherein during transport of said fluid, said fluid is converted from a liquid phase into a gaseous phase. 14. The method in Claim 11, wherein said gaseous fluid upon entering said bore hole or cavity produces a substantially horizontal interface during movement down said borehole or cavity. 15. The method in Claim 11, wherein said digital readout means further provides readout of the change in the weight of said fluid as said fluid moves down said borehole in predetermined intervals. O PI TU7E S EET ^ 16. The method in Claim 11, wherein the factors of known weight of said fluid within a certain interval in said borehole, together with the known pressure and known temperature of said fluid, is entered into a com¬ puter and converted into a pictorial readout of the con¬ figuration of said borehole or cavity within said given interval. 17. The method in Claim 11, wherein said temperature of said nitrogen within said borehole is in a range of 70 # - 110'F. 18. An apparatus for determining the shape of a borehole or cavity, which comprises: a. a fluid medium, said medium comprising liquid nitrogen or some other inert fluid; b. container means for containing said fluid medium under a given pressure; c. means for determining the weight of said fluid within said container; d. pump means for transporting- said fluid from said container down into the borehole or cavity to be mea¬ sured, said fluid during transport converted to gaseous nitrogen; e. digital readout means for indicating the change in weight of said fluid within said container during the transport of said fluid converted to gas into said bore¬ hole or cavity; f. means, suspended within said borehole, for indi¬ cating the linear vertical movement of said fluid down SUBSTITUTE SHEET said borehole at predetermined intervals within said borehole; and, g. chart means for visually plotting the movement of said fluid down said borehole or cavity as a measure¬ ment of the configuration of said borehole and cavity. 19. The apparatus in Claim 18, wherein said weighing means comprises: a. a pair of vertically disposed support beams intergrally connected to the ends of a horizontally dis¬ posed member, said support beams movable upward and downward; b. means for connectedly engaging said container onto said horizontally disposed member; c. a weight cell intermediate said horizontal mem¬ ber and said container for indicating the total weight of said container; and d. hydraulic means for hydraulically moving said suspended container upward and downward during said pro¬ cess. 20. The apparatus in Claim 18, wherein said digital readout means also records the change in weight of said nitrogen within said container during the measuring pro¬ cess. 21. The apparatus in Claim 18, wherein the movement of said fluid from said container into said borehole converts said fluid from a liquid phase to a gaseous phase at a temperature range of 70 * to 110*F. SUBSTITUTE SHEET

Inventors: BROUSSARD PAUL P, FAUL DONALD J, GRANGER DONALD W, BROUSSARD, PAUL, P., FAUL, DONALD, J., GRANGER, DONALD, W.
Applicants: BROUSSARD PAUL P, FAUL DONALD J, GRANGER DONALD W, BROUSSARD, PAUL, P., FAUL, DONALD, J., GRANGER, DONALD, W.
Application year: 1983
Main classification: E21B47
IPC codes: E21B47, G01B13