bluuebunny/crossref_metadata_2025 huggingface dataset:
Evolution and Differences of Directional and High-Performance Downhole Motors
Authors: Makohl F. , Jurgens R.
Published: December 2007

The introduction of downhole motors to the drilling industry has helped to reduce costs and to develop new drilling technologies.

The idea of using a downhole motor directly on top of the bit instead of turning the whole drill string is not new. The first commercial downhole motor was a turbine, but it turned too fast for most existing bits and applications, especially directional drilling. So other ideas were tried.

An electric downhole motor was experimented with, but it failed because of power transmission problems. Finally, the positive displacement motor (PDM) was developed. Like the turbine, the PDM converts the hydraulic power of the mud flow into mechanical power at the bit. But it turns slower, and thus has become the preferred downhole motor for most operations.
An Engineering Approach to Stabilization Selection
Authors: McKown G. K. , Williamson J. S.
Published: December 2007

A means of selecting stabilizers based on applications and drilling conditions is presented. Experimental wear data and computer analyses of the effects of stabilizer design on bottom hole assembly performance are offered. Useful flowcharts summarizing the papers conclusions on stabilizer and reamer selection are also given.
Liner Cementing Techniques and Case Histories Offshore Western Gulf of Mexico
Authors: Hebert R. N.
Published: December 2007

Liner cementing success in Tenneco Oil Company's Western Gulf of Mexico Division increased from 44% between 1979-1982 to near 80% for the period of 1983-1985. The improvement in cementing success can be partially attributed to implementation of a planned liner top squeeze after the bottom of the liner has been cemented conventionally. This is accomplished by running a retrievable squeeze packer above the liner run-in tool. This method of liner cementing was pioneered and had been used successfully for over ten years by Superior Oil Company. It was studied and adapted by Tenneco with the emphasis placed on improving liner cementing success through the designation of a liner cementing specialist. Twenty-three liners have been run using this technique. Case histories with successes and failures will be reviewed in this paper.
One-Piece, Forged, Heavy Wall Drillpipe: Built Stronger for Tougher Drilling
Authors: Schock W. H. , Santucci R.
Published: December 2007

Rotary-forged, heavy wall drill pipe is composed of a homogeneous one-piece forging of AISI 4145 Modified low alloy steel. This integral forging eliminates the weld at the tool joint, has high strength steel pipe and has a center upset the same diameter as the connection upsets. Continuous-line heat treating increases the depth of hardening to enhance the mechanical properties of the integrally forged material. Whether used in compression, in tension or at the neutral point for drilling vertical or directional holes, this new drill string member will increase fatigue life and reduce stress corrosion-cracking tendencies over commonly used lower strength welded pipe.
Personnel Safety While Handling High-Density Brines
Authors: Krause D. C.
Published: December 2007

Specific safety apparel, handling techniques, and safety planning are needed to assure safe effective working conditions on any rig site where high density brines are used. Pre-spud safety meetings and on the rig training should be given to all personnel directly involved with the project.

High density brines have different properties than do drilling muds, and consequently, should be handled differently for safety reasons. Brine properties that differ from those of drilling muds are discussed and the affected safety procedures are expanded upon.

Personal wearing apparel is of utmost importance when handling brines. Chemical splash goggles, rubber gloves, and rubber boots should be mandatory when handling brines. Rubber aprons, slicker suits and dust/mist respirators should be added for specific conditions.

Eye wash fountains and drench showers should be installed on the rig near high splash risk areas.
Method for Improving Hydrocarbon/Water Ratios in Producing Wells
Authors: Dunlap D. D. , Boles J. L. , Novotny R. J.
Published: December 2007

Production of unwanted water has consistently burdened the industry since the costs of lifting, separating, and disposing of produced water make oil and gas production less profitable. Previous methods for reducing water production have involved the sequential pumping of two or more materials to form plugs within the formation to control water flow. These materials have been neither effective nor selective in-reducing only the flow of water.

The recent introduction of new water control chemicals, which are designed to, reduce the flow of water while not effecting hydrocarbon flow have experienced limited success. One reason for the minimal success rate has been the inability of these polymers to withstand shear. In addition, poor candidate selection has created a high volume of unsuccessful treatments, causing operators to shy away from their use.

A selective, one component system using a new amphoteric polymeric material (APM) has been developed which has the ability to reduce the effective permeability to water while retaining the formation permeability to oil or gas.

In addition a candidate selection technique used to predict the likelihood of success of a water control treatment is presented.
Productivity Decline in Gravel Packed Wells After Acidizing
Authors: McLeod H. O.
Published: December 2007

The current interpretation of gravel pack productivity decline seems to focus on dispersion and plugging with formation fines, especially after acidizing. This paper presents an alternate explanation. Gravel may be flushed from perforations during acidizing into acidized formation voids, gravel may move into acidized gravel pack voids in the screen-casing annulus during production start-up, or tunnel voids may have existed prior to acidizing as a result of poor gravel placement during gravel pack execution. Production start-up rate controls how formation sand enters partially filled voids after acidizing. A controlled production rate allows formation sand to enter the tunnel above the gravel so that a more conductive parallel alignment of sand and gravel in the tunnel is created.
Underbalanced Perforating in a Closed System
Authors: Seanard K. C.
Published: December 2007

Several recent papers have been written expounding the use of tubing conveyed perforating as, a completion technique. (See Ref. 1,2) These papers propose the use of underbalanced perforating to remove perforating damage. This paper will present a recommended method of perforating underbalanced in a closed system. Perforating in this manner allows the use of high pressure differentials to surge the perforations while at the same time limiting influx into the wellbore and allowing control of the well.
Polymer Shear Mixer: A Device for Improving the Quality of Polymer Viscosified Brines
Authors: Ashton J. P. , Nix C. A.
Published: December 2007

A shear apparatus has been developed to improve the quality of polymer viscosified brines. Application of the device to mix the polymer into the brine results in a viscous brine that can be cost effectively filtered. The rheological properties of the fluid remain virtually unaltered when compared to similar brines mixed by conventional methods.
Development of Fuyu Fractured Sandstone Reservoirs by Water Injection
Authors: Chen Yanzheng
Published: December 2007

The Fuyu fractured sandstone reservoir is characterized by low permeability and medium high crude viscosity. There is insufficient natural energy because of its shallow depth of burial. The field was put into development in 1970 under solution gas drive. Water injection was started in 1973 and an overall adjustment of the development program was made in 1982.

The following methods have been used successfully according to the geologic features of the field as well as the problems occurring during development: To supply more energy by active water injection.The rapid decline of the production and reservoir pressure under solution gas drive has been stopped and gradually restored.Well-developed vertical fractures and horizontal bedding in the overlying shales result in a good permeable zone. Under high injection pressures, water runs from the reservoir formation into these layers and causes swelling of the clay minerals in them, so that a lot of casing damage occured with a serious effect on the production of the field. Thus it is important to control injection pressure and to take comprehensive measures to eliminate the casing damage. Good results have been obtained.The data from non-invasion cores and from newly drilled wells have been used to study the status of water flooding, the reserves affected by current status development program and the distribution of the remaining oil in the reservior. Based on such a study, the adjustment wells are located in the areas where the majority of the remaining oil exists. The zones with medium and low Water cut have been perforated for production, thus more reserves will be put into water drive production.According to the characteristics of fracture development in the reservoir, a linear injection pattern has been used to restore the reservoir pressure and to prevent water channeling through fractures. Good results have been achieved.
Development by Waterflooding of Maxi Deep Reservoir with Low Permeability
Authors: Wang Zhizhong , Zhang Xuyuan
Published: December 2007

Maxi oilfield – a deep seated reservoir, located in the central part of North Dagang structural belt of Huanghua Depression, Is an Integrated dome anticline with major axis extending in a NE direction, being steep in the north and gentle in the south. The structure covers an area of 11 square kilometers with a vertical closure of 130 meters. The main pay zones are Ban II and III, T1 of paleogene, being a suite of bar sand and beach sand deposits of deep littoral facies. The depth of burial of the reservoir is 4,000 meters with relatively poor physical properties. The porosity is 13.3% and permeability is 13.6 md. It is of argillaceous cementation with a fair sorting. Rock compaction and secondary growth are obvious.

The distribution of oil, gas and water are mainly controlled by the structure. The oil-water contact is quite clear, being 3,900 meters in Ban II and 3,970 meters in Ban III. The crude property is good with low specific gravity of stock tank crude (with an average value of 0.8408) and low viscosity (6.2 cp/50°C on an average). The asphaltene content is low (4.98 percent on an average). The reservoir temperature is high (149°C). The presssure coefficient is also high (1.473/10m) with a large pressure difference between reservoir and saturation pressure (186 atm.). The underground viscosity of crude is abnormally low (0.38 cp). Therefore, it is a structural reservoir with an abnormally high pressure, low permeability and is undersaturation.

Exploration of this field began in 1965. In 1978, commercial oil flow was encountered and put into development with a 500m 5-spot well pattern in 1980. By the end of 1981, it was put on stream. Its recovery rate has been kept high during the four-year period of production. A series of development techniques have been used for deep-seated reservoir, such as protection of the reservoir from mud contamination, through tubing perforation under negative pressure differential, water injection under high pressure (400 atm), development through separated technique, deep pentrated fracturing, and a closed oil and gas gathering and transportation system, etc. thus achieving good oilfield development results. There were 21 oil wells and 5 injection wells by the end of 1984. The daily production was 473 tons and cumulative production reached 780,000 tons. The overall water cut was 6.5%. Daily injection of water was 613 m3 in five injection wells and the cumulative water injected reached 721,000 m3. The production capacity of oil wells was quite good and waterflooding was carried out normally.
A Study on Some Problems in the Calculations of Corrosion Fatigue Life of Structural Members of an Offshore Platform
Authors: Fang Huacan , Dong Shouping , Chen Zhenxin
Published: December 2007

This paper presents the results of research and tests on some problems involved in calculations of corrosion fatigue life of structural members of a platform, using the theory and method of fracture mechanics.

According to random vibration theory, the method and a programme for making the random sea wave spectrum and the method for calculating the transfer function of a structural member of a platform are given. The method and programme for composing the spectrum of random stress amplitudes by random sea wave spectrum and transfer function is proposed; finally, for counting the load cycles in estimating the fatigue life, a new method of cycle counting is proposed using two parameters of stress ratio and stress amplitude directly from the random stress spectrum.

In order to evaluate the fatigue life, experiments on constant amplitude and random fatigue crack growth rate have been carried out; the Paris' formula has been modified; a programme for the experimental data processing has been given; and the method and an example for calculating residual corrosion fatigue life of the structural member of a platform, based on fatigue damage criteria dadn in terms of the crack growth rate are given, and is illustrated by a sample calculation
Investigation on the Applications of Statistical Formation Drillability
Authors: Yin Hongjin
Published: December 2007

An equal probability correlation of bit types and formation drillability grades has been established with experimental and statistical methods. The variation of drillability with depth has been studied. The empirical equations of drillability varying with depth is checked with a parametric equation of drilling rate. Useful information of macroscopic formation drillability can be derived from statistical analysis of abundant individual microbit drillability testing results.
A Study of Sulfide Scavenger
Authors: Chen Chuanlian , Huang Wenqin
Published: December 2007

A sulfide scavenger CS 6-1 has been developed to protect the drilling tool from sulfide stress cracking, electrochemical corrosion and corrosion fatigue. The desulfurization efficiency and corrosion inhibition rate of the scavenger were measured for laboratory and field muds. Its desulfurization efficiency exceeded 98% and the corrosion inhibition rate was up to 70-90%. The addition of an appropriate amount of CS 6-1 doesn't affect the mud characteristics. Field tests have shown that the desulfurization efficiency of CS 6-1 in alkaline muds is better than that of sponge iron and Milgard scavengers.
Heat Flow During Steam Injection Into a Fractured Carbonate Reservoir
Authors: Dreher K. D. , Kenyon D. E. , Iwere F. O.
Published: December 2007

Steam injection into fractured carbonates has been examined in the laboratory and with a fully implicit reservoir simulator. These studies showed that significant oil can be recovered from matrix elements when hot water or steam is injected into fractures. Heat is rapidly replenished to fractures and heat conduction into the matrix plays a major role in matrix heating with a resulting increase in the rate of oil release. At steam temperatures carbonates decompose to produce a significant amount of CO2 which further enhances the recovery rate.

Carbonate disks were flooded in the laboratory with hot water and steam. Oil recovery from competent as well as fractured disks increased as injection temperature increased. Oil recovery from fractured disks approached 30% 0IP at 200°F even though pressure differentials were small. In other experiments, CO2 con-centration in effluent gas was determined. One mole of CO2 was produced for each mole of H2O injected at steam temperatures.

Reservoir simulations were accomplished using two kinds of porosity/permeability grid blocks. Fracture grid blocks were continuous from injection to production wells and accounted for less than 0.5% of the total reservoir volume. Oil recovery and water/oil ratios were dependent on matrix grid block size, steam Injection rate, initial saturations and distributions, and CO2 generation. Oil recovery increased with in creasing steam injection rates, however, water/oil ratios were high. These results show that there is an optimum steam injection rate for a specified reservoir volume and matrix grid block size. The rate of heat conduction from fracture to matrix is the controlling factor.
Measurement of Steam Quality, Mass Flow Rate, and Enthalpy Delivery Rate Using Combined Neutron Densitometer and Nozzle
Authors: Woiceshyn G. E. , Yuen P. S. , John H. , Manzano-Ruis J. J.
Published: December 2007

Accurate measurement of steam quality and enthalpy delivery rate at the wellhead is required for efficient operation and reliable evaluation of enhanced recovery projects that utilize steam injection. Steam distribution through manifolds and tees can lead to uneven splitting and a wide variation of steam quality and enthalpy delivery rate for different wells fed from the same boiler. A field-grade densitometer, which is based on the principle of thermal neutron transmission, has been developed and tested for measurement of steam quality at the wellhead. The meter is non-intrusive, portable, robust, easy to operate, safe for field use and accurate. By combining the meter with a flow measuring device, such as a flow nozzle, accurate measurements of steam quality, mass flow rate and enthalpy delivery rate at the wellhead are possible.

This paper describes the densitometer's principle of operation and results from recent calibration tests conducted over a wide range of field conditions.
Effect of Capillary Number on the Residual Saturation of a Three-Phase Micellar Solution
Authors: Delshad M. , Bhuyan D. , Pope G. A. , Lake L. W.
Published: December 2007

One of the most important physical relationships in a low interfacial tension IFT process is the capillary desaturation curve (CDC). The CDC is the relation between residual phase saturation and the ratio of viscous to local capillary forces (capillary number). Despite its importance, a complete set of experimental CDC for low IFT fluids has not been reported in the literature.

We report CDCs for a low IFT two-and three-phase brine/oil/surfactant/alcohol mixture in Berea sandstone cores. These are the first CDCs reported for a three-phase micellar solution. There are six possible CDCs for three phase flow. We have measured (l)-residual oil to microemulsion, (2)-residual microemulsion to oil, (3)-residual brine to microemulsion, and (4) -residual microemulsion to brine. These CDCs have been measured by stepwise increases in flow rate at a fixed IFT of 0.7 μN/m. These data showed that the microemulsion phase is the most strongly trapped which implies that the microemulsion is the wetting phase--even more wetting than the excess brine.

We also include CDC data for a two-phase (brine/oil/alcohol) mixture of fresh and Dri-Film treated Berea sandstone. The data in fresh core are in good agreement with the micellar CDC data.

Continuous displacements of radioactive tracers have also been run during these steady-state, single-phase flows. The tracer analysis provided essential information on both phase saturations and dispersivities.

The single-phase dispersion coefficients for tracer in oil, brine, and microemulsion phases showed the well-known increase with phase frontal velocity that is typical for single-phase flow of brine reported in literature. No values for oil or microemulsion have been previously reported. The tracer dispersivities showed little dependence on phase saturation.
High-Pressure Combustion Tube Tests
Authors: Prasad R. S. , Slater J. A.
Published: December 2007

High pressure air fireflooding may have some benefits hitherto not observed at lower pressures. Combustion tube tests were conducted at pressures approaching 3,000 psi. Special start-up procedures were used, especially for the wet burns, to make the testing representative and also minimize the transient effects. The tests indicated: Immiscible displacement of oil by carbon dioxide is an important mechanism at these pressures.The heat-scavenging ability of the water injected along with the air is, as expected, still appreciable at these pressures.
Comparison of Recovery and Economics for Oxygen and Air Fireflood in Canadian Heavy Oil Areas
Authors: Dugdale P. J.
Published: December 2007

The heavy oil pools of Alberta and Saskatchewan can be grouped into four reservoir types: Lloydminster, Wainwright, Basal Quartz and Bakken.

This study reviews briefly the recovery attainable in these reservoir by secondary and non-fireflood processes, and then evaluates in situ combustion using both oxygen and air in dry and wet fire-floods. Recent studies by a national energy agency have shown that fireflood is the best enhanced oil recovery process that can be used in heavy oil reservoirs, with anticipated recoveries of 30% of the original oil in place. The paper reports the computed recoveries using the Tejas, Nelson-McNeil, Fassihi and Brigham methods and then presents an incremental recovery correlation due to the immiscible CO2 flood established ahead of the oxygen firefront.

The experimental evaluation of key fireflood parameters is examined and compared to those predicted by correlations available in the literature. Air/oxygen requirements, fuel laydown and rate of firefront advance, as well as oxidant injectivity are discussed; recommendations are made on the laboratory and field testing needed prior to implementation of in situ combustion.

An economic comparison of both air and oxygen firefloods, which considers the recoveries and field costs for the two processes, has been carried out for a demonstration pilot in a Wainwright type field.
A Study of Caustic Consumption by Clays
Authors: Huang L. , Yang P. , Qin T.
Published: December 2007

The reactions of alkaline with clay minerals in reservoir rocks have been investigated under static conditions.

With the help of the titration, the determinations of the irreversible chemical kinetics of the reaction of alkaline with 3 kinds of clay minerals and quartz were carried out at 60°C. High concentration sodium hydroxide and orthosilicate were used in these treatments for a time period as long as 1000 hours. The supernatants were analyzed for hydroxide, (Si), (Al) etc. and precipitated solid parts at different time periods were analyzed by X-ray differaction and other methods. The results show that the irreversible consumption of sodium hydroxide is the highest on montmorillonite and it is not a simple reaction. The consumption is very fast at first and slow down gradually. The alkali consumption can not be described by a single first-order reaction. The reaction is associated with the formation of new minerals which are mostly zeolites and the consumption of dissolved (Al) in later reaction, other than (Si), was observed.

On the other hand, fast reversible alkaline consumption by ion exchange was observed at room temperature accompanied with the reaction controlled by chemical kinetics. H/Na exchange adsorption isotherms are Langmuir type in shape. The reversible alkali consumption is also the highest on montmorillonite. The test results show that it can be decreased by using a high salinity preflush and a subsequent low salinity caustic solution injection.
A Method To Convert Multiple-Shot Section Openhole Completions Into Cased-Hole Completions With Zonal Isolation
Authors: Darr C. D. K. , Brown E. K. , Murphey J. R.
Published: December 2007

A method to convert multiple shot section open hole completions into cased hole completions has been developed and tested. This method provides zonal isolation between shot sections thus helping prevent injection fluid loss to non-pay intervals. The process, called "Puddle-Pack", involves formulating a permeable resin fill material and placing the material in the shot open hole to fill the large voids. The excess material is then drilled out and underreamed to allow a liner to be run and cemented in place. This paper details the necessity for the development of the process, design requirements, laboratory pretesting of the sand-resin mixture, remedial procedures, data demonstrating zonal isolation and profile improvement, and economic advantages of converting these wells to cased hole completions.
The Value of CO2 to Today's Producer
Authors: Jankowski D. J. , Wolsky A. M.
Published: December 2007

The cost of carbon dioxide, CO2, is the principal component of the cost of miscible flooding for enhanced oil recovery, EOR. This paper presents an engineering-economic framework that shows how to estimate the amount an EOR project can afford to pay for delivered CO2, This amount (here called "permissible cost"), depends on many factors, both geologic and financial. We show how the effects of these factors combine to produce the permissible cost, with the emphasis on its sensitivity to flooding efficiency, oil price, and internal rate of return. We use parameters given in the National Petroleum Council's Enhanced Oil Recovery reports (1976 and 1984) to illustrate the results for two hypothetical reservoirs. These results display variability that should be expected from different fields.
An Economic Evaluation of Waterflood Infill Drilling in Nine Texas Waterflood Units
Authors: Reviere R. H. , Wu C. H.
Published: December 2007

This paper examines the profitability of past waterflood infill drilling programs. The project data is from the Texas Railroad Commission files, and includes large carbonate and sandstone reservoirs such as the Wasson (San Andres) Field and the Big Wells (San Miguel) Field. All of the reservoirs were subject of intensive reservoir engineering and geologic study by the oil companies prior to initiation of the infill drilling project. The permeability of the reservoirs averages 8.8 md and ranges from .65 md to 27 md. The porosity averages 10% and ranges from 7% to 18.6%. The depths range from 1220 to 1525 meters with the deepest at 2130 meters.

Because of the large capital cost required for drilling and operating additional wells, it was not clear whether the infill drilling programs had recovered enough additional oil to be good investments. In spite of the variability of external factors such as the cost of wells and price of oil, all of the projects studied obtained at least an acceptable economic return, the average discounted profit to investment ratio was 2.0, and the average incremental oil per well was 15 thousand cubic meters. Most of the calculated rates of return exceeded 30%. The net present value at 15% after taxes ranged from $580,000 to $32 million dollars. Thus these waterflood infill drilling projects have generally been very successful.
Use of Emulsions for Mobility Control During Steamflooding
Authors: French T. R. , Broz J. S. , Lorenz P. B. , Bertus K. M.
Published: December 2007

It is widely known that the economics of many steamflood enhanced oil recovery (EOR) projects are strongly affected by steam override (gravity segregation) and steam channeling. The economic performance of many steamfloods can be improved if an effective method of plugging the steam override or channeling zones is utilized. Traditionally, foam blocking techniques have been utilized with variable success to achieve these goals.

In this paper, laboratory results from research at the National Institute for Petroleum and Energy Research on the development of an emulsion blocking technique for the correction and control of steam override and channeling are presented. Coreflood experiments were performed to demonstrate the effectiveness of emulsion blocking at temperatures ranging from ambient to 194°C. The permeability reduction of various types of cores using externally produced emulsions and in situ generated emulsions was measured for light and heavy crude oils. Externally produced emulsions injected into oil-free cores reduced the permeability by 86 percent at 110° and 77 percent at 160°C. Injection of externally produced emulsions into cores containing residual oil, where some of the pores are already blocked, resulted in 30 to 91 percent reduction in permeability. Emulsions generated in situ using caustic to emulsify Wilmington crude oil achieved a 43 percent reduction in effective permeability with the absolute permeability of this core being 1,400 md. In both cases of injected and in situ emulsions, the emulsion block was thermally stable, and no degradation of the block was observed after injection of many pore volumes of water.

The strong possibility that foamblocks as heretofore applied may have an emulsion blocking component to the overall plugging mechanism is discussed. Foams created with known foaming agents were contacted with various crude oils, and emulsified droplets within the liquid interfaces were observed.

Work leading to the development of a field pilot test and ultimate commercialization of the process is presented. Laboratory studies for a planned field pilot were performed using sandpacks made from Kern River unconsolidated core and emulsion produced from the oil and water available in that field.
A Semianalytical Model for Hot Water Surfactant Flooding in a Linear Reservoir with Heat Losses
Authors: K’Vella D. E. , Dehghani K. , Ostermann R. D.
Published: December 2007

This study presents a semi-analytical model of combined injection of hot water and chemical in a linear homogeneous medium. The model takes into account lateral heat losses and horizontal heat conduction for two phase flow with surfactant travelling in the water phase only. Using the correlations available in the literature, the model considers the dependence of the chemical adsorption on temperature, and the relative permeabilities variation with temperature and interfacial tension. The physical dispersion of the chemical and the change of heat capacities and densities with temperature were assumed to be negligible.

The reduction in interfacial tension between aqueous and oelic phase, combined with an Increased mobility achieved at high temperatures was shown to enhance the recovery efficiency of a standard hot water flooding process. The sensitivity of the recovery process with different cases of heat transfer was investigated. The results show that neglecting lateral heat losses and horizontal conduction overestimates the recovery, while neglecting horizontal conduction leads to an underestimation of the oil recovery.
Relative Permeability from Centrifuge Data
Authors: Firoozabadi A. , Aziz K.
Published: December 2007

The drainage of a wetting phase (say oil) by a non-wetting phase (say gas) may be simulated in the centrifuge by two liquids. Such experiments were conducted on a number of cores and they are discussed in a companion paper. In this paper we consider two of the cores with available capillary pressure data. Two forms of the relative permeability models are selected and the parameters of these models are obtained by history matching with a numerical simulator developed for this study that properly accounts for the capillary pressure and the boundary conditions in centrifuge experiments. It is shown that; (1) recoveries can be matched with two – and maybe even more – very different sets of relative permeability curves; (2) recoveries are sensitive to the parameters of each relative permeability model; (3) excellent history match is possible with arbitrarily small capillary pressure values, but the resulting relative permeabilities are different from those obtained with experimental values of the capillary pressure; and (4) late time predictions can be improved by using a linear relationship for the wetting phase relative permeability below some arbitrary value of the wetting phase saturation.

It is concluded that the capillary pressure (Pc) term should not be ignored in obtaining relative permeability curves from centrifuge data. Analytical or numerical models that do not properly include Pc or ignore Pc should be used with caution.
Delayed Crosslinked Gels: Their Role in Aqueous Foam Fracturing
Authors: Freeman E. R. , Bilden D. M. , Hossaini M.
Published: December 2007

Foam fracturing with a base fluid of delayed crosslinked gel has expanded the use of foams in fracture stimulation and greatly improved job success rates. Foamed delayed crosslinked gels allow the placement of much higher proppant concentrations in the fracture than foamed linear gels. Also, the fracture fluid efficiency is greatly enhanced allowing better control of downhole fracturing parameters (e.g. leakoff) critical for successful stimulation.

Laboratory results indicate that the foaming of a delayed crosslinking gel increases apparent viscosity, improves proppant transport capabilities, and extends fluid loss properties beyond those of foamed linear gels.

More than 200 treatments have been completed in various formations in California, Texas, and Oklahoma. A review of local formation characteristics and treatment conditions are discussed regarding the application and successful use of a crosslinked versus conventional linear gel foam.

Noteworthy is that crosslinking the gelled phase of a foam system requires limited modification of current foam fracturing procedures or equipment.
Some Parameters Influencing the Formation and Propagation of Foams in Porous Media
Authors: Friedmann F. , Jensen J. A.
Published: December 2007

Experiments were run to investigate the effect of surfactant concentration, injection rate, foam quality, oil saturation, and rock absolute permeability on the formation and propagation of foams in Berea sandstones and Ottawa sandpacks.

First, constant pressure unsteady-state gas-liquid relative permeability experiments were conducted in Berea sandstone for varying residual saturations of synthetic oil. It was found that high oil saturations can hinder the formation of foam (no substantial decrease in the gas phase relative permeability). In such cases, some of the oil must first be displaced from the core before a foam can form.

Other experiments were performed by flowing preformed foams into cores at various conditions. The foams were preformed at high rates representative of tubing or sandface rates. They were injected into the porous medium at lower rates representative of near wellbore conditions (1.5-5 m from the wellbore) but not of in-depth reservoir conditions. Results showed that the foam propagation rate was significantly affected by rock permeability and injected foam texture. In high permeability sandpacks (40-50 darcies), the foam propagated at the same rate as the liquid phase. Foam propagation rates decreased substantially in lower permeability media.
Susceptibility of Petroleum Reservoir Sands to Water Damage, Powder River Basin, Wyoming
Authors: White E.J. , Baptist O.C. , Land C.S.
Published: December 2007

The productivity of some oil sands may be reduced if invaded by fresh water during drilling, completion or workover operations. The most common cause of formation damage is swelling clay minerals in the sand. Damage is also caused by movement of loose particles or increased water saturation.

The susceptibility of water damage of the producing sands in the basin was estimated by using several laboratory tests. The results of the different tests generally indicated about the same degree of sensitivity, suggesting that sensitivity can be determined by using only one or two tests. However, the other tests are also useful because each illuminates a different aspect of capillary behavior.

Zones exhibiting a high degree of sensitivity in wells were usually found to be interbedded with zones having moderate to low sensitivity. Also, the average sensitivity of the more sensitive sands varied significantly from field to field, making it desirable to determine the sensitivity of questionable sands in each field early in the development program.

Of the 10 sands studied, four exhibited either high or moderate sensitivity; of these four, three are of Upper Cretaceous age, and the other one is Jurassic. Except for the Jurassic, all sands older than Upper Cretaceous have low sensitivity.

Introduction

Well Completions and Water Damage

The productive capacity of some oil wells is seriously reduced when filtrate from water-base mud invades the formation during the drilling or completion of the well. Sands that are susceptible to this type of damage are sometimes called water sensitive. Any one or more of several factors may be responsible for water damage; these are swelling clays, particle transportation, low-permeability water block and water block in oil-wet sands. Of these, no doubt the most common type of sensitivity is that caused by clay minerals [either by swelling or transportation], and it is this type with which this study is primarily concerned.

All clay minerals undergo some, though differing, amounts of swelling when wetted with water; therefore, if present in sufficient quantity, they may impart some degree of sensitivity to sands.
ES100PC: A Multiphase Flow/Nodal Analysis Program for IBM Personal Computers
Authors: Stoisits R. F.
Published: December 2007

ES100pc is a multi-phase flow pressure drop/systems analysis program designed to run on the IBM XT or AT. It has the capability to perform pressure loss calculations in wellbores, flowlines and pipelines. Inflow performance curve calculations are also available. Pressure loss in flowing or gas lifted wells may be computed. A number of multiphase flow pressure drop correlations are available. The user may select correlations or enter data for the physical properties. Inflow performance curves may be calculated using a variety of correlations.

An input data preprocessor is available to assist the user in building his dataset. This processor allows the user to either create, edit or execute a dataset through a series of prompting messages.

ES100pc is a scaled down version of a mainframe program. Over the past several years the mainframe program has been used by hundreds of engineers within ARCO with good, results. The PC version yields results comparable to the mainframe program while allowing the engineer the autonomy and economy of a micro-computer.
A New Algorithm for Hyperbolic Decline Curve Fitting
Authors: Spivey J. P.
Published: December 2007

A new algorithm for hyperbolic decline curve fitting is presented. The new algorithm is self starting, and converges very rapidly. The algorithm minimizes the sum of squares of the deviations of the logarithm of the producing rate from the predicted value.
The Use of Microcomputer Spreadsheets to Perform Scoping Analysis for Engineering Applications: Waterflood Candidate Evaluation
Authors: Engler R. A.
Published: December 2007

Much of Reservoir Engineering work involves relatively simple calculations. High powered reservoir simulators and data manipulation routines are important, but not vital in most cases to be able to make a sound economic decision. The use of spreadsheet programs such as LOTUS 1-2-3* enables any engineer to quickly set up and perform many analyses in a very efficient manner, using equations available in any good text on reservoir engineering. The results of a scoping analysis then form the basis for a decision to use more sophisticated analysis methods. Another very significant advantage of using a spreadsheet for this type of work is that output is formatted as the spreadsheet is built. Conventional BASIC or FORTRAN programs require significant additional effort to present results in a suitable format.

An example application illustrating useful techniques would be the analysis of waterflood potential in a field. Examples are shown of spreadsheet templates used for normalizing relative permeability curves, generating fractional flow information, performing log calculations, estimating fluid properties, and calculating waterflood performance using displacement efficiency methods. Once the project is approved, a unitization formula can also be negotiated using the spreadsheet to determine unit working interest based on various parameters and weighting schemes.

This example is intended as a demonstration of the potential uses of a spreadsheet to quickly perform engineering calculations and present the results in a suitable format without elaborate formatting routines. Using techniques such as these allows an economic decision to be made with a minimal engineering investment.
The Use of Public Domain and Inexpensive Software in Education
Authors: Eskijian M. L.
Published: December 2007

Public domain and inexpensive software can be used as a teaching tool in petroleum engineering to enhance the student's capabilities, as well as prepare him for more advanced and sophisticated applications in the workplace. This paper will describe a "toolbox" of applicable software, totalling less than $75, including the disk media. With this "toolbox" the student can become familiar with software for database management, spreadsheet calculations, word processing, graphics and a compiled Pascal language with a built-in editor.
Well Test Engineering Software With Built-In Expert Advice
Authors: Erdle J. C. , Archer D. A. , Stiff T. J. , Callihan M. C.
Published: December 2007

Well Test engineering is a complex function requiring both technical knowledge (facts) and experience (beliefs and heuristics). A large number of computer programs have been developed by E&P companies, service companies, consultants and software vendors to assist engineers and technicians in performing some of the tasks which are considered essential to successful well test engineering problem-solving. The distinguishing feature of a majority of these programs is their emphasis on technical features, rather than overall problem-solving capabilities. In general, as the level of program technical sophistication increases, the problem-solving efficiency of the users decreases, thus presenting a software selection dilemma to users and their managers. One solution to this dilemma is to combine the desired level of technical sophistication with problem-solving assistance in the form of procedures and constraints recommended by "experts" in the theory and application of well test engineering technology. This approach effectively places an "applications" expert over the shoulder of the program user, who is the real expert in the "behavior" of the wells and reservoirs being tested. The solution described in the paper evolves from the emerging science of artificial intelligence and is referred to as "expert systems" technology. The paper describes expert systems technology and its application to a well test engineering software package being developed through the combined efforts of an experienced well test engineer and a computer programming specialist. The concepts introduced enhance the utility of well testing by making expert well test engineering problem-solving capability available to non-expert engineers and technicians.
North Sea Score Card
Authors: Castle G. R.
Published: December 2007

A number of the North Sea oil and gas fields have been developed and produced to a point where it is now possible to compare their historical performance against their original projections. Furthermore, revised forecasts, (which are based on more reliable data) that have been prepared recently for these fields, can also be compared against the original projections. This type of analysis suggests that none of the fields studied for the purpose of this paper merit high scores for good performance. For example: 87% of the fields studied had cost overruns.87% were late in achieving first production.87% have not produced the quantity of oil and gas through the end of 1983 as was originally expected.52% are not expected to achieve the peak levels of production originally forecast.83% have spent more on operating costs through the end of 1983 than was originally expected.
Technique for Considering Fluid Compressibility and Temperature Changes in Mini-Frac Analysis
Authors: Soliman M. Y.
Published: December 2007

An analytical technique has been developed to consider fluid compressibility and temperature changes when making mini-frac analyses.

Mini-frac tests in which the effects of compressibility and changing temperatures are ignored can produce results that are as much as 75% in error. However, techniques for mini-frac analysis presented in current petroleum engineering literature are based on the assumption that fracturing fluid is incompressible and isothermal in nature.

This paper examines the effects that fluid compressibility and temperature changes have on mini-frac analysis by presenting field cases analyzed by the method developed. The analysis was performed using both PK and CZ models as presented in literature.

An example analysis using the PK model showed that when both temperature and compressibility effects are ignored, errors of 300% in calculated fluid loss coefficient and 75% in calculated fracture length are encountered. The same example using CZ models gave 200% and 33% errors in fluid loss coefficient and fracture length, respectively.

Correcting for temperature and compressibility effects is considered through the use of "effective pressure drop," or pressure drop the mini-frac would have exhibited if ideal conditions had prevailed. Developing this concept allows the use of already developed type curves. The approach is analogous to pseudo pressure in well testing. When only compressibility effect is considered, only the magnitude and not the shape of ΔP versus dimensionless time graph is changed. Correcting for both temperature change and compressibility changed both shape and magnitude of the curve. It has been observed that a better match was obtained after such correction.
Fractal Distributions of Reservoir Heterogeneity and their Influence on Fluid Transport
Authors: Hewett T. A.
Published: December 2007

Theories of fluid flow in heterogeneous porous media show that their transport properties are determined by the structure of spatial correlations in the permeability distribution. When the range of these correlations is comparable to or larger than the fluid flow path, solutions of the convective-dispersion equation with an effective dispersivity augmented to account for the dispersive effects of reservoir heterogeneity do not provide accurate predictions of the transport characteristics of the medium. Measurements of property distributions in sedimentary environments show a fractal character with long range correlations. Evaluation of the influence of fractal distributions of permeability on oil recovery process performance requires simulation on a distributed field of properties with a correlation structure matching that in field measurements. The geometric properties and spatial correlation structure of fractal distributions are discussed and methods for measuring the fractal character of field data and synthesizing fields with a similar correlation structure are reviewed.
Development of a Chemical Process for Sand Control
Authors: Burger J. G. , Gadelle C. P. , Marrast J. R.
Published: December 2007

The paper describes the continuous experience gained from the laboratory evaluation and field testing of an original chemical sand consolidation process.

The process involves the successive injections of (a) a polymerizable organic material and proprietary catalysts, and (b) a limited volume of oxygen-containing gas. In some cases, a preflush sequence is recommended beforehand. The binding agent is formed by a chemical reaction between the organic material and oxygen. The existence of a gas flow in the reacting volume contributes to preserve the rock permeability. The laboratory work which led to the optimization of this process is briefly described. Cores are obtained with very good resistance to compression and with essentially unaffected permeability.

The operating procedure and the results of typical field tests are discussed in this paper. Wells were successfully treated in both oil and gas fields. After the treatment, sand-free production has been demonstrated, for durations from several months for the most recent tests, to several years for the older ones. No decrease in productivity index has been observed.