bluuebunny/crossref_metadata_2025 huggingface dataset:
A Three-Part Study of NMR Longitudinal Relaxation Properties of Water-Saturated Sandstones
Authors: Kenyon W. E. , Day P. I. , Straley C. , Willemsen J. F.
Published: December 2007

Borehole measurements of the nuclear magnetic resonance (NMR) properties of rocks have been of interest for many years, especially for estimating permeability. This paper presents laboratory measurements of the NMR properties of water-saturated rocks and shows that permeability can be estimated well with expressions of the form ϕ4T12, where T1 is the relaxation time constant of the longitudinal nuclear magnetization of hydrogen nuclei. Different methods of representing the laboratory-measured T1 curves are shown, including a new one called the stretched-exponential representation. An improved method for estimating T1 parameters from borehole measurements that can be used with either old or new representations is presented.
Effect of Temperature on Wave Velocities in Sands and Sandstones With Heavy Hydrocarbons
Authors: Wang Zhijing , Nur Amos
Published: December 2007

A laboratory investigation was made of the effects of temperature on wave velocities in sandstones and unconsolidated sand saturated with heavy hydrocarbons. The large decreases of the compressional and shear velocities in such sandstones and sand with increasing temperature suggest that seismic methods may be very useful in detecting heat fronts in heavy hydrocarbon reservoirs undergoing steamflooding or in-siju combustion.
In-Situ Heat System Stimulates Paraffinic-Crude Producers in Gulf of Mexico
Authors: Ashton J. P. , Kirspel L. J. , Nguyen H. T. , Credeur D. J.
Published: December 2007

A thermal stimulation process that generates downhole heat currently is being used to stimulate oil wells in the Gulf of Mexico. The crude produced from these shallow wells is highly paraffinic. Previous attempts to stimulate these wells with paraffin solvents and acid systems have been unsuccessful. The in-situ heat process has yielded 10-fold production rate increases and payout times of less than 1 week.
Effects of Spreading and Nonspreading Oils on Foam Propagation Through Porous Media
Authors: Lau H. C. , O’Brien S. M.
Published: December 2007

Experiments show that a spreading oil increases the time for foam generation and decreases the speed of foam propagation in a porous medium. It also breaks a foam faster than a nonspreading oil. These findings may be important in interpreting results of different foam displacement experiments and therefore surfactant selection.
Minimum Miscibility Pressure Prediction With Equations of State
Authors: Benmekki E. H. , Mansoori G. A.
Published: December 2007

Prediction of the minimum miscibility pressure (MMP) of the vaporizing gas drive (VGD) process is modeled by use of an equation of state (EOS) with different mixing rules joined with a newly formulated expression for the unlike three-body interactions between the injection gas and the reservoir fluid. The comparison of the numerical results with the available experimental data indicates that an EOS alone overestimates the MMP. When the EOS is joined with the correct version of the van der Waals mixing rules and the unlike three-body interaction term, however, the MMP will be predicted accurately.
Dog-Leg Control in Directionally Drilled Wells
Authors: Wilson G.J.
Published: December 2007

WILSON, G.J., MEMBER AIME, CONTINENTAL OIL CO., HARVEY, LA.

Review of difficulties experienced in drilling directional wells in the offshore Grand Isle Block 43 field showed most failures of drill pipe, drill collars and casing to have been associated with excessive dog-legs. Alleviation of difficulties was approached by synthesizing theoretical and practical concepts in a planned dog-leg control program. Preventive measures necessary to control dog-leg severity and corrective measures used to reduce unacceptable dog-legs are discussed. When other measures fail, deliberative measures as outlined can be employed alter the probable cumulative fatigue damage to be sustained by the drill pipe has been determined. Results of a program successful in virtually eliminating problems stemming from excessive dog-legs indicate that control of dog-leg severity in directional wells is feasible and will cause no decrease in the over-all drilling rate.

Introduction

Prompted by an increasing frequency of drill pipe, drill collar and casing failures, a study of 50 directional wells representing 592,000 ft of hole, including 444,000 ft of deviated hole, drilled in the offshore Grand Isle Block 43 field was conducted in early 1965. A number of drill pipe washouts and six keyseating problems were recorded and a detailed review was made of 16 failures which had required fishing effort in 10 of the 50 directional wells drilled prior to June, 1965. These problem wells are exemplified by Wells G and F for which pertinent data are shown in Figs. 1 and 2. Data pertaining to all of the 16 failures are summarized in Table 1. Inspection of these data shows most of the problems to have been associated with dog-legs in excess of theoretical limits suggested by Lubinski and excessive dog-legging is indicated to have been concomitant with whipstocking in several of the problem wells. Results of the investigation agreed with those reported by Schenck who had concluded that problems could be expected when dog-leg severity exceeded limits proposed by Lubinski. Since Schenck had demonstrated the desirability and feasibility of drilling directional wells without excessive dog-legging, a dog-leg control program was established in June, 1965 for wells drilled in the Grand Isle Block 43 field. This paper reviews the methods by which theoretical and practical concepts were synthesized to develop a program of preventive, corrective and deliberative measures which virtually eliminated problems stemming from excessive dog-legs in directional wells. Dog-legs of a magnitude causing no damage are referred to as permissible dog-legs and larger dog-legs are referred to as excessive or severe dog-legs.

JPT

P. 107ˆ
Effect of Cyclic Formation-Pressure Changes on Permeability
Authors: Aggour M. A. , Malik S. A. , Harari Z. Y.
Published: December 2007

Unconsolidated sandpacks of various mesh sizes and consolidated Berea sandstone cores were subjected to repeated pressurization/depressurization cycles under constant confining pressure, after which their absolute and relative permeabilities were measured during the relaxation periods. The permeabilities of the sandpacks decreased as a result of the pressurization, and the reduction in permeability increased as the magnitude and duration of the applied net core pressure increased. The permeabilities continued to decrease with successive pressurization/depressurization cycles, albeit at a decreasing rate. After a finite number of cycles, no further reduction was observed. The number of cycles needed for stabilization was inversely proportional to the duration of the pressurization cycles and was found to be lower for fine sand than for coarser sand. Some recovery in permeability was achieved after the cores were allowed to relax; however, the cores were permanently damaged.

Berea sandstone cores also exhibited reductions in permeability as a result of pressurization/depressurization cycling. The reduction increased in direct proportion to the magnitude and duration of net core pressure. However, no reduction in permeability was observed below peak net core pressure levels of <3,500 psi [<24.1 MPa]. It was found that no significant recovery of permeability had taken place after the cores were allowed to relax at low pressure, indicating that the cores were permanently damaged.

Two models are proposed for explaining the mechanisms of permeability reduction under the present test conditions for both unconsolidated sand and consolidated cores.
Reaction Kinetics of Fuel Formation for In-Situ Combustion
Authors: Abu-Khamsin Sidql A. , Brigham William E. , Ramey Henry J.
Published: December 2007

Chemical reactions believed to cause fuel formation for in-situ combustion have been studied and modeled. A thin, packed bed of sand/oil mixture is heated under nitrogen flow at linearly increasing temperatures, simulating the approach of a combustion front. Analysis of gases produced from the reaction cell revealed that pyrolysis of crude oil in porous media goes through three overlapping stages: distillation, mild cracking (visbreaking), and severe cracking (coking). Expressions that govern the rates of the two cracking reactions are derived, and a technique is outlined to obtain initial estimates for their parameters from the experimental data. The parameters of a proposed distillation function, as well as refined estimates for the cracking reaction parameters, are obtained by non-linear regression methods based on an overall kinetic model.

Successful matching of the experimental data, including the total amount of fuel deposited, was achieved with this model. It was found that fuel formation was a result of two successive cracking reactions that the oil undergoes at temperatures above 280° C [536°F]. Also, distillation of crude oil at temperatures below 280°C [536°F] played an important role in shaping the nature and extent of the cracking reactions. The operating pressure and the rate of heating of the sand/oil sample were found to affect the fuel-formation process only through the influence exerted on distillation. Clay minerals showed a catalytic effect on the cracking reactions, especially coking. Finally, the asphaltene fraction of a crude oil was found to correlate with the fuel content of that oil.
Coastal Barrier Reservoirs
Authors: Richardson J.G. , Sangree J.B. , Sneider R.M.
Published: December 2007

Coastal barriers are long, narrow, wave-built, sandy islands parallel to the shore. Part of the island has a beach, but may parallel to the shore. Part of the island has a beach, but may have sand dunes and areas of vegetation above the high-tide line. A lagoon or estuary is behind the barrier on the protected side away from the ocean, as shown in Fig. 1. Coastal barrier reservoirs can hold major accumulations of oil and gas. Coastal barriers can build by three major processes: addition of sand washed onto the beach from breaker bars, addition on one end by sand washed from the other end and moved by riptides, and deposition of sand into the lagoon by waves breaking over the barrier during storms. Tidal channels that form at the ends of the barriers tend to migrate laterally and fill with sand from the barriers (see Fig. 1). Wind-blown (aeolean) dunes are usually minor parts of the barrier deposits. Galveston Island, offshore Texas, is a good example of a modern coastal barrier. Waves in the Gulf of Mexico have sufficient energy to transport and deposit fine-grained sand on Galveston Island. (Fine-grained sand is the coarsest sand available in upper Texas coastal waters.) Other examples of modern coastal barriers are found in the Gulf of California, where medium-sized sands are deposited. An example of an ancient deposit was found in the Elk City field, where the barrier beach was composed of well-sorted gravel and coarse sand.

P. 1127
Sand-Rich Deltas
Authors: Richardson J.G. , Sangree J.B. , Sneider R.M.
Published: December 2007

Technology Today Series articles provide useful summary informationon both classic and emerging concepts in petroleum engineering. Purpose: To provide the general reader with a basic understanding of a significantconcept, technique, or development within a specific area of technology.

The preceding article in the Technology Today Series (Jan. 1989 JPT. Pages12–13) described the general processes of building deltas. The present articlefocuses on the reservoir characteristics of high-energy sand-rich deltas. Theseform when the wave and tidal action is sufficiently strong to rework thedeposits brought in by distributary channels before their burial. The principaltypes of sand bodies and highest-quality reservoir rocks in a delta arechannels and stream-mouth bars. Also present are the sheet sands deposited on adelta front and localized sand bodies left in minor crevasse deposits adjacentto channels during floods. While these bodies have definite areal relationshipsto one another during the process of building a lobe on the delta, theirthree-dimensional relationships become complex as the deltas build seaward orshift positions along the shoreline. Thus, a channel active during a laterbuilding cycle may cut into or may lie over stream-mouth bars, delta-frontsheets, or crevasse sands left earlier. Fortunately, the various sand bodieshave different distributions of permeability and different responses to logs sothat they can be identified. The coarsest sand is left at the base of a channeland silt and clays are left at the top. Typical gamma ray log responses andpermeabilities measured in cores show depth profiles in Fig. permeabilitiesmeasured in cores show depth profiles in Fig. 1a through c in sands leftupstream, onshore, and near mouths of distributary channels, respectively. Thelow gamma ray log responses at the bases show that little clay or shale ispresent. The increased gamma ray log response toward the tops of the channelsreflects the presence of more clay and shale. Similarly, the largest grainsizes and highest permeabilities are measured in cores from the base anddecrease upward.

p. 89
Treatment-Fluid Selection for Sandstone Acidizing: Permeability Impairment in Potassic Mineral Sandstones
Authors: Bertaux J.
Published: December 2007

Drastic formation permeability reduction can result from certain rock-mineral/treating-fluid reactions. In potassic mineral sandstones, conventional HCl/HF acid treatments are proved to induce damage from byproduct precipitation, contrary to fluoboric acid (HBF4) treatments. Laboratory tests are described that provide a methodology for selecting the appropriate treatment fluid on the basis of formation/treating-fluid compatibility and damage removal.
A Correlation of the Viscosity of Hydrocarbon Systems With Pressure, Temperature and Composition
Authors: Little J.E. , Kennedy H.T.
Published: December 2007

An empirical equation for the prediction of the viscosity of several pure paraffin hydrocarbons and nitrogen is presented. It involves temperature, pressure and six constants of the material, and it applies reliably to both liquids and gases. The equation is similar in form to van der Waal's equation of state. For the paraffin hydrocarbons methane through n-hexane and nitrogen, an average absolute deviation of 1.9 percent was obtained on 1,006 data points described in the literature by 14 authors. When this equation is extended to complex, liquid hydrocarbon mixtures, a correlation was obtained with an average absolute deviation of 9.9 percent.

Introduction

Equations describing the flow of gas and liquid through porous media contain the viscosity coefficient of the fluid. If other pertinent variables remain constant, the volume rate of flow is inversely proportional to this coefficient. In dealing with condensate fluids and volatile oils, however, the compositional effects resulting from changing pressure materially affect the viscosity. The effect of compositional changes also may be significant in certain secondary recovery or pressure maintenance processes, notably miscible displacement or gas injection. Early attempts to describe the performance of reservoirs utilized a volumetric material balance method wherein gas and liquid in the reservoir were identified as produced gas and liquid at the surface. This method of analysis proved adequate for reservoirs at moderate temperature and pressure that contained gas with moderately low amounts of condensable materials. The volumetric material balance procedures for "black oil" reservoirs leave much to be desired when applied to condensate and volatile oil reservoirs because phase behavior and compositional changes the relatively more important in these cases. The alternative is a compositional material balance, which in turn, requires a correlation of properties of the reservoir fluid with composition. This paper supplies this correlation in regard to viscosity, for reservoir crude oils.

REVIEW OF LITERATURE

The literature contains many empirical equations describing the effects of composition, temperature and pressure on the viscosities of pure liquids and binary liquid mixtures. However, the applicability of a majority of these equations is limited to very low pressures and to a small number of systems. Most of the, when applied to complex hydrocarbon systems, are of little value. The lack of utility of the majority of equations results from the fact that they were developed to show the separate effect of temperature, pressure or composition on viscosity, but not to predict the viscosity as a function of all three variables. And with the few exceptions noted below, they were developed to apply to much simpler systems than hydrocarbon mixtures.

P. 157ˆ
Advanced Techniques Improve Liner Cementation in North Sea Wells: An Operator's Experience
Authors: Buchan R. , Little M. T. S.
Published: December 2007

Improvements in liner cementation in the North Sea are being made through optimization of cementing practices and the use of advanced technology, which includes liner rotation during hole conditioning and cementing. This paper reviews our experiences and discusses key aspects of liner rotation, including equipment selection, job design, and implementation. Comparison of cement-bond logs (CBL's) with those from nonrotated-liner cement jobs shows that liner rotation during cementing can greatly improve results.
Estimation of Effective Permeabilities in the Lower Stevens Formation of the Paloma Field, San Joaquin Valley, California
Authors: Desbarats Alexander
Published: December 2007

Simulation programs used in reservoir studies require effective gridblock permeability values representing spatial averages over large volumes of formation. Within such volumes, most reservoir rocks exhibit a considerable degree of heterogeneity, with permeability measurements often varying over several orders of magnitude. A satisfactory method for averaging permeabilities must consider not only the magnitude of permeability variations, but also the variations of permeability in space. Using experimental histograms and variograms to describe the heterogeneous permeability field within gridblocks, a Monte Carlo technique is used to estimate effective permeability. The method is illustrated by an example with actual permeability data from the lower Stevens formation of the Paloma field in Kern County, CA. Experimental downhole variograms of permeability showed a large nugget effect at short lags and a longer correlation structure with a range of 100 ft [30 m]. For the particular distribution and spatial correlation structure of these data, effective horizontal and vertical permeabilities were found to be respectively higher and lower than the geometric mean. Calculated effective permeabilities were found to be relatively insensitive to assumptions regarding the horizontal range of spatial correlation. This lack of sensitivity is caused by the large nugget effect or random short-range correlation structure. Effective permeabilities obtained with an approximate analytical relation were compared with effective permeabilities calculated numerically.
Impulse Testing
Authors: Ayoub J. A. , Bourdet D. P. , Chauvel Y. L.
Published: December 2007

This paper proposes a new method for evaluating hydrocarbon wells. The formation is subjected to a rate impulse created by briefly flowing the well or injecting into the formation. The pressure response to an ideal rate impulse (i.e., to an instantaneous source of strength unity) is given by the derivative of the pressure response to a conventional step-rate change. This general solution is used in developing an interpretation method based on recently published type curves of the derivative of pressure.

Impulse™ testing is particularly useful for wells that do not flow to the surface and for wells where extended flow may not be desirable (because of sand problems, for example). Applied in conjunction with underbalanced perforating, this method provides a low-cost evaluation of the reservoir and wellbore condition. Several field examples are presented to illustrate the analysis technique.
Model Selection for Well Test and Production Data Analysis
Authors: Watson A. T. , Gatens J. M. , Lane H. S.
Published: December 2007

The estimation of reservoir properties from production or pressure data measured during production or well tests is an important process for reservoir characterization and performance prediction. A key step in that process is the selection of a reservoir model for use in the interpretation of the data. We develop a procedure for selecting the most appropriate model from a pool of candidates. A parameter estimation algorithm is used to evaluate parameters within candidate models. Statistical measures are then used to select the most appropriate model.

We demonstrate our procedure for model selection with actual well test data and production data from the Devonian shale. We show how our methodology can be used to evaluate whether certain reservoir features can be identified from measured production or pressure data. We also present a test for evaluating whether independent estimates of reservoir properties are consistent with measured pressure and production data.
A New Technique for Analyzing Buildup Tests From Hydraulically Fractured Wells
Authors: Rahim Zillur , Lee W. John
Published: December 2007

This paper presents a new iterative technique for interpreting early-time pressure-buildup data for hydraulically fractured wells. The technique uses a modified square-root-of-time analysis with permeability and fracture-length correction curves generated from Cinco-Ley et al.' s solution to flow equations for finite-conductivity fractures. The method is applicable to low-permeability reservoirs where conventional methods of analysis are difficult to apply.
Production-Systems Analysis for Fractured Wells
Authors: Hunt James L.
Published: December 2007

Production-systems analysis has been in use for many years to design completion configurations on the basis of an expected reservoir capacity. The most common equations used for the reservoir calculations are for steady-state radial flow.

Most hydraulically fractured wells require the use of an unsteady-state production simulator to predict the higher flow rates associated with the stimulated well. These high flow rates may present problems with excessive pressure drops through production tubing designed for radial-flow production. Therefore, the unsteady-state nature of fractured-well production precludes the use of steady-state radial-flow inflow performance relationships (IPR’s) to calculate reservoir performance. An accurate prediction of fractured-well production must be made to design the most economically efficient production configuration.

It has been suggested in the literature that a normalized reference curve can be used to generate the IPR’s necessary for production-systems analysis. However, this work shows that the reference curve for fractured-well response becomes time-dependent when reservoir boundaries are considered. A general approach for constructing IPR curves is presented, and the use of an unsteady-state fractured-well-production simulator coupled with the production-systems-analysis approach is described. A field case demonstrates the application of this method to fractured wells.
A Mathematical Model for Pressure Evaluation in an Infinite-Conductivity Horizontal Well
Authors: Rosa Adalberte J. , Carvalho Renate de Souza
Published: December 2007

A mathematical model was developed to study the transient pressure behavior in a well with an infinite-conductivity horizontal drainhole in an infinite slab reservoir. The physical model includes a fluid of small and constant compressibility flowing through an infinitely large anisotropic reservoir with upper and lower impermeable boundaries. The analytical solution is obtained by applying the concepts of instantaneous sources and Green's functions.

We discuss the uniform-flux model, a special case of the infinite-conductivity model, and present a simple way to use it to calculate the pressure at the wellbore face. We suggest that the pressure for the infinite-conductivity case can be evaluated with the uniform flux model at a fixed point along the wellbore with an error of less than 1 % for combinations of the various parameters that may be encountered in real situations. We show to what extent the accuracy of the model will be affected by neglecting gravitational effects.
New Analytical and Numerical Solutions for the Radial Convection-Dispersion Problem
Authors: Tang D. H. E. , Peaceman D. W.
Published: December 2007

New analytical and numerical solutions are presented for the radial convection-dispersion differential equation with a velocity-dependent dispersion coefficient. The finite-difference numerical scheme is shown to have negligible numerical dispersion for this problem. Very close agreement is obtained between the analytical and numerical solutions. The effect of the type of boundary condition used at the wellbore is discussed.
A New Computational Approach to the Miscible Displacement Problem
Authors: Hatzlavramidis Dimitri T.
Published: December 2007

A 2D miscible displacement computer code based on a pseudospectral method that uses Chebyshev expansions and a grid adaptive to the position of the front was developed. In this method, the effect of physical dispersion is explicitly included, while the effect of numerical dispersion is greatly suppressed. The code was shown to have exceptional convergence, accuracy, stability, and computational economy. It accurately predicts the position and sharpness of the displacement front for ID miscible and immiscible displacements. The code also predicts oil recoveries and breakthrough times for 2D miscible displacements with unfavorable mobility ratios that are in agreement with experimental data and is shown to be effective in resolving details of viscous fingering phenomena.
Typical Features of a Multipurpose Reservoir Simulator
Authors: Quandalle P. , Sabathier J. C.
Published: December 2007

This paper describes a new three-dimensional (3D), three-phase, multipurpose reservoir simulator. An extensive description is given of the dual-porosity facility. Three user-selected options available for computing the material transfers between matrix and fractures are developed and discussed. The most sophisticated option accurately accounts for the capillary, gravity, and viscous forces. A simplified thermodynamical package is also presented and examples are given.
The Relationship Between Radius of Drainage and Cumulative Production
Authors: Johnson P. W.
Published: December 2007

At least six radius-of-drainage formulas have been published. These formulas are reviewed and correlated on the basis of the fraction of net production for which each accounts. Numerical results are summarized in an equation for calculating the radius of drainage that corresponds to a given fraction of the net production.
A Practical Evaluation of Nondestructive Tubular Inspection Units: Methods and Results
Authors: Reynolds Bruce W. , Gill L. Owen
Published: December 2007

This paper describes a program for evaluating flaw-detection capabilities of electromagnetic inspection (EMI) and ultrasonic inspection (UT) units used in oil-country tubular goods (OCTG) inspection. The test program involves use of two 7-in. [17.78-cm] joints of casing; each contains various OD and ID defects. The test procedures are similar to those used by other major operators, but the scope, design, and quality-control measures of Chevron's program make it unique. Results are presented for the 73 evaluations conducted to date, which indicate a two-to-one superiority of UT units in flaw-detection capabilities. The relatively poor performance of EMI inspection prompted re-evaluation of the use of this type of service for OCTG body wall inspection.
BOP Shear Rams for Hydrogen Sulfide Service
Authors: Canal J. R.
Published: December 2007

The shear rams in a blowout preventer (BOP) are critical components of the drilling system, which is expected to shear drillpipe and to seal the wellbore in all types of drilling fluids. The brittleness of high-strength tool steels when exposed to wellbore fluids containing H2S has been recognized for many years by the drilling industry. The development in recent years of high-strength materials that are resistant to hydrogen embrittlement has made possible the manufacture of H2S-resistant shear rams. This paper describes the fabrication of such shear rams. The cutting edge is made from a cobalt base (UNS R30035) and an iron-based superalloy (UNS S66286) joined by an electron-beam (EB) welding process. The discussion continues with the shearing tests of API 5A Grades E, G, and S-135 drillpipe of two wall thicknesses with a 13%-in. [346-mm], 10,000-psi [69-MPa] working-pressure (WP) ram BOP.
Methods for Handling Drilled Gas in Oil-Based Drilling Fluids
Authors: O’Bryan P. L. , Bourgoyne A. T.
Published: December 2007

This paper presents calculation methods for predicting the behavior of drilled-gas contamination of oil-based drilling fluids. The methods are verified by experiments conducted in a 6,000-ft [1828.8-m] test well. This paper also presents field-handling procedures developed with the calculation methods.
Comparison of Field and Laboratory-Simulated Drill-Off Tests
Authors: Bourdon J.-C. , Cooper G. A. , Curry D. A. , McCann D. , Peltier B.
Published: December 2007

Field drill-off test results are compared with data from laboratory simulations. A simple theory for analyzing drill-off tests is developed. The weight-on-bit (WOB) decay with time is close to exponential, but large threshold WOB's, resulting from poor weight transmission downhoie, are sometimes observed in field tests.
Planning and Operational Requirements for a Shallow-Objective, High-Angle Well in the Gulf of Mexico
Authors: Christian D. B.
Published: December 2007

This paper is a case history of a highly deviated exploratory well in East Cameron Block 378. This well was difficult because it is located in the middle of a shipping fairway. Planning and engineering requirements for the successful completion of the well are discussed. Highlights include the directional plan, casing design, measurement while drilling (MWD) for directional information and formation evaluation, drilling fluids, and rig selection.
Surface Equipment Cleanup Using In-Situ Heat
Authors: Collesi Jacqueline B. , Scott Thomas A. , McSpaddon Hal W.
Published: December 2007

A chemical system capable of generating heat in situ has been used to remove hydrocarbon deposits, mainly paraffin, from surface equipment and flowlines in the U.S. gulf coast. The treatments resulted in increased production throughout the structures. The chemical system, treatment design, case histories, and results are discussed.
Formation Damage Related to Hot Oiling
Authors: Barker K. M.
Published: December 2007

Hot oil has been used to remove paraffin deposits almost as long as oil has been produced. It is still the most widely used procedure for paraffin removal in use today because of its relative simplicity of application, immediate results, and low cost per application. These apparent benefits have obscured the damage that hot oil can cause when used to clean downhole production equipment.

Formation damage caused by hot oiling is related to the physical characteristics of the oil used, the source of the oil, the formation temperature, and the hot-oil process. Potential problems are discussed and suggestions made to minimize or to eliminate them. Laboratory tests are presented for determining whether a crude will cause formation damage during hot oiling. Case histories of successful cleaning of hot-oil formation damage are also given.
A Kinetic Model of CO2 Generation and Mineral and Isotopic Alteration During Steamflooding
Authors: Cathles L. M. , Schoell Martin , Simon Ralph
Published: December 2007

CO2 is commonly produced during steamflooding. In higher-temperature steamfloods the amount of CO2 produced is such that the only viable source is carbonate minerals. We show by reference to CO2 concentrations in natural geothermal systems that in most common rocks and sediments, CO2 is generated naturally under hydrothermal (~572°F) conditions by the dissolution of carbonate minerals. CO2 solubility is a strong positive function of temperature and, at 572°F, is more than sufficient to account for high CO2 concentrations like those encountered at Chevron's Buena Vista (BV) Hills steamflood pilot test. A linear kinetic model is developed to describe chemical equilibration and CO2 generation in the hot parts of the reservoir. The model also describes CO2 removal through carbonate precipitation in the cooler parts of the rock formation where the fluid moves ahead of the thermal front. Changes in carbon isotope concentration are included in the model. The small difference between the 13C in the produced gas and the source carbonates at BV Hills suggests that little CO2 is precipitated as carbonate within that reservoir, a prediction that can be tested by poststeamflood coring.
Evaluation of Microbial Systems in Porous Media for EOR
Authors: Bryant Rebecca S. , Douglas Jonell
Published: December 2007

The use of microorganisms to enhance oil recovery has become a technically feasible technology for production from stripper wells (those that produce less than 10 B/D [1.6 m3/d]). As a result of microbial growth and the production of CO2 and/or chemicals, oil recovery can be effectively increased in certain reservoirs with temperatures and salinities hospitable to microorganisms.

Research at the Natl. Inst, for Petroleum and Energy Research has led to development of laboratory facilities for evaluating microbial systems for microbial enhanced oil recovery (MEOR) applications. Results from microbial core studies using Berea sandstone have shown that bacteria can vary greatly in their ability to recover residual oil after waterflooding, giving from 7.5 to 71 % recovery efficiency. The type of core encapsulation did not affect oil recovery. Variations in rock permeability from 134 to 1,920 md indicated that some microorganisms may exhibit a better recovery efficiency in lower-permeability cores. The results also show that gas production by microorganisms is not the only factor affecting oil recovery; some bacteria that produce surfactants but no gas could provide equally efficient additional oil recoveries. Likewise, the type of surfactant also makes a difference; two species that produce surfactants can vary in recovery efficiency. Another contributing mechanism to microbial oil mobilization may be by increasing areal sweep efficiency from microbial growth. A comparison of oil recovery efficiencies between microorganisms using a medium-to-light-gravity oil (Delaware-Childers) and two heavy oils (Wilmington, CA, and Chaffee, CA) indicates that MEOR may be effective for heavy oils as well as light oils. Correlations are presented between the recovery efficiency of a particular microbial species and its ability to mobilize crude oil in etched-glass micromodels.
Effects of Shutting In Injectors on Steamflood Performance
Authors: Hong K. C.
Published: December 2007

The effects of temporarily shutting in steam injection wells on oil recovery by steamflooding were studied with a steam injection simulator. Both heavy- and light-oil steamflood situations were considered. A one-eighth of a five-spot model representing the two types of reservoirs was used to study the effects of shutting in the injector for up to 8 months on the oil production performance during the shut-in period and following the resumption of steam injection.

The simulation results show that temporarily shutting in injectors is not detrimental to overall oil recovery. For each type of reservoir (heavy or light oil), the cumulative oil production at a limiting instantaneous steam/oil ratio (SOR) of 10 was essentially the same regardless of the length of injector shut-in. The cumulative SOR at the end of the project life also remains the same, regardless of the length of shut-in. Shutting in the injector, however, prolongs the project life, increasing it by about the length of shut-in for the heavy oil and by more than the length of shut-in for the light-oil case.

This paper compares oil production performances for steamflood projects operating under different shut-in scenarios and recommends strategies to cope with the changing economic environment.
Reliability of Laboratory Measurement of Porosity in Tight Gas Sands
Authors: Luffel D. L. , Howard W. E.
Published: December 2007

A study was conducted to verify or to improve the routine laboratory procedures normally used to measure porosities of cores from tight gas sands. After routine analysis of 242 core plugs from the Travis Peak formation in east Texas, 20 of the plugs were analyzed for porosity by two additional laboratories. Each of the three laboratories had problems with their results that normally would have gone unnoticed but were recognized because of disagreement with results from the other laboratories. After reruns, agreement was excellent, with a standard deviation of about 0.25 porosity units (p.u.) when comparing one laboratory against another. To improve reliability of routine porosity measurements, recommended practices and quality-control procedures are presented.
The GRI Staged Field Experiment
Authors: Holditch S. A. , Robinson B. M. , Whitehead W. S. , Ely J. W.
Published: December 2007

The Gas Research Inst.'s (GRI's) Tight Gas Sands Program has been involved with research on low-permeability formations during the past 4 years. The main focus of the research has been to improve the general understanding of producing tight reservoirs, while a specific focus has been to advance the technology involving hydraulic-fracture geometry. The unique aspect of this research is that the laboratories have been actual gas wells completed in the Travis Peak formation in east Texas.

To extend the development of technology fully, GRI has planned four staged field experiments (SFE's) from 1986 through 1989. The SFE program provides the opportunity to collect a wealth of data that cannot be obtained from normal cooperative research wells. The purpose of this paper is to summarize all the tests and data collected on the first SFE and to present the available results from the analyses of these data.
A New Approach for Constructing Derivative Type Curves for Well Test Analysis
Authors: Onur Mustafa , Reynolds Albert C.
Published: December 2007

Recently, type curves based on pressure derivatives have become a highly popular method for analyzing well test data. Typically, these type curves represent a log-log plot of dimensionless pressure and the derivative of dimensionless pressure vs. dimensionless time. This work presents a new general procedure for constructing type curves based on a new combination of dimensionless pressure and the derivative of dimensionless pressure. The procedure can be used to construct type curves for all standard problems encountered in well testing. The new type curves always have good character so that nonuniqueness problems sometimes encountered in type-curve matching are eliminated; thus, the type curves constructed by our method should improve our ability to obtain accurate estimates of reservoir parameters by type-curve matching. The basic procedure is used to construct new type curves for wellbore storage and skin problems and for fractured wells (uniform-flux and infinite-conductivity). These type curves are constructed so that the vertical scale of the dimensionless derivative groups is automatically aligned with the vertical scale of the field-data derivative groups; thus, type-curve matching of field derivative data is accomplished by moving the field data plot only in the horizontal direction. This automatic alignment of the vertical scales simplifies type-curve matching and also is advantageous for determining whether field data actually represent the solution assumed by a given type curve.
Review of U. S. Oil and Gas Production -- 1965
Authors: Lindsly R.R.
Published: December 2007

Introduction

The petroleum industry supplies approximately 73 per cent of the nation's energy requirements, and domestic capital and exploration expenditures total more than $6 billion annually. The producing segment of the industry accounts for around 60 per cent of these capital expenditures, and domestic production amounts to approximately 80 per cent of the nation's liquid raw material supply. The producing industry is important from the standpoint of national security, and its reserve producing capacity, Jan. 1, 1966, was approximately 2.7 million bbl of crude oil and natural gas liquids daily, based on IPAA estimates. The productive capacity of natural gas, Jan. 1, 1964, as estimated by NPC in its 1965 report, indicates 57.7 billion cu ft/D of capacity over and above the average production for 1963. Total petroleum demand in 1965 averaged 11,490,000 B/D, up 473,000 or 4.3 per cent from 1964. Gasoline, which makes up approximately 41 per cent of demand, experienced a healthy 3.9 per cent increase. Total petroleum supply in 1965 averaged 11,482,000 B/D. Of this total, domestic crude production (68.0 per cent of supply) averaged 7,804,000 B/D, up 2.5 per cent; natural gas liquids production (10.5 per cent of supply) averaged 1,210.000 B/D, up 4.8 per cent; and imports of crude and products (21.5 per cent of supply) averaged 2,468,000 B/D, up 9.3 per cent from 1964. Demand for natural gas continued in upward trend in 1965 as reflected by production which totaled 16.3 trillion cu ft, or a 6.5 per cent increase over the 15.3 trillion cu ft produced in 1964. Fig. 1 shows supply trends of petroleum and natural gas from 1956 to 1965.

Reserves

To supply the ever-increasing demand for petroleum and natural gas, adequate reserves must be maintained through continuous exploratory efforts, development drilling and improved recovery techniques. Therefore, it is pertinent to note the changes in underground inventory during 1965. Proved reserves of crude oil at year-end 1965 stood at 31.4 billion bbl, up 1.2 per cent from the previous year. Although the change is small, it is the second consecutive year that crude reserves have posted an increase. However, the reserves-production (R-P) ratio in 1965 was 1 1.7: 1, down slightly from the previous year. It was the fifth straight year of decline and reflects the failure of reserves to keep pace with production which has grown at the rate of 2.0 per cent for the past five years. Proved reserves of natural gas liquids at year-end 1965 were 8.0 billion bbl, up 3.6 per cent from 1964. After trending downward since 1958, the R-P ratio leveled off at 14.5:1, the same as in 1964.
Downhole Maintenance of Subsea Completions
Authors: Simpson D. M. , Pearce J. L.
Published: December 2007

This paper describes some of the work performed in Phase 1 of a multiphase joint industry program to investigate a down-hole maintenance system for subsea completions that is both reliable and cost-effective. Phase 1 covered concept selection, leaving Phases 2 and 3 to cover critical component design and further development, respectively. The approach taken in Phase 1 to accomplish the program's purpose was to identify and then to study those concepts for transporting maintenance tool strings through the water column and into the subsea tree that eliminated the requirement of a drill vessel for surface support.
Recovering Oil by Retorting a Nuclear Chimney in Oil Shale
Authors: Lombard D.B.
Published: December 2007

A method is proposed for recovering oil by retorting oil shale shattered by deep underground nuclear explosions. Because most of the oil will be obtained from chunks of oil shale with maximum dimensions exceeding 1 ft, retorting times of up to several weeks are needed for complete recovery. A study of the heat economy of the retorting process in an underground nuclear chimney suggests that the nuclear detonation itself and the subsequent controlled combustion of residual carbon in retorted oil shale will provide ample energy. The proposed method is shown to be thermally efficient. A 5-ft diameter, 12-ft high aboveground batch retort has been constructed for the experimental retorting of mixtures of oil shale particle sizes. Low rates of air and recycle gas, low-retorting temperatures and slow combustion front advance have characterized its operation. In spite of imperfect mist-separating equipment, recoveries of about 60 percent of Fischer assay have been obtained. The particle size distribution of 30 gal/ton oil shale has not been appreciably altered by the retorting. The operating conditions of a nuclear chimney retort will be defined by the recycle gas-to-air ratio and the overall rate of gas injection. Determination of optimum operating conditions will be complicated by the large number of factors involved. However, the proposed technique appears to be a promising one for recovering the oil from thick, deep, oil shale deposits.
Interaction of Natural Convection and Gravity Segregation in Oil/Gas Reservoirs
Authors: Jacqmin David
Published: December 2007

The distribution of chemical components in reservoirs can be significantly affected by diffusional segregation caused by gravity. This segregation, however, can be opposed by convective mixing. Parallel-flow solutions are presented that shed light on the interaction of these two processes. The solutions are used to explain results of numerical calculations of convection-diffusion in model rectangular reservoirs.
Mechanisms of Miscibility Development in Hydrocarbon Gasdrives: New Interpretation
Authors: Novosad Z. , Costain T. G.
Published: December 2007

This study concerns the mechanism of miscibility development in multiple-contact-miscible (MCM) gasdrives. Many low-pressure, rich-gas floods, traditionally assumed condensing processes, are shown to be vaporizing or (upper) liquid-extraction drives. It is shown that the solvent phase behavior at reservoir conditions determines the mechanism of miscibility development and that the rich-gas drives in low-temperature reservoirs are mostly condensing processes, while the liquid-extraction mechanism prevails in high-temperature reservoirs. The equation-of-state (EOS) simulations support this new interpretation of rich-gas-drive mechanism. Direct experimental evidence is also provided. The misuse of pseudoternary diagrams and failure to recognize their limitation when applied to multicomponent systems are shown often to lead to a false indication of a condensing processing. This adversely affects interpretation of experimental data (such as interpretation of miscibility in slim-tube displacements), and thus miscible solvent design.
Emeraude Vapeurs A Steam Pilot in an Offshore Environment
Authors: Couderc Bernard M. , Verpeaux J. F. , Monfrin Dominique , Quettler Lisette H.
Published: December 2007

Adverse conditions prevail in the Emeraude field offshore Congo on the West African coast, including shallow (200 to 500 m), very heterogeneous reservoirs and 100-mPa·s oil at reservoir conditions. In 1983, a steamdrive pilot was begun in two superposed and independent reservoirs to estimate recovery rate and oil/steam ratio (OSR). The shallow reservoirs required tilted conductor pipes, a tilted rig, and adapted pumping units on one platform, while steam production equipment had to be located on a second platform because of the distance to shore. After 3 years of steam injection, the incremental recovery rate was promising and the OSR was 0.30 vol/vol in the pilot area. Some wells outside the five-spot pilot also showed oil-rate increases. Numerical simulations of the pilot behavior were made with a thermal pseudocompositional simulator.
Interpretation of Thermal Well Falloff Testing
Authors: Stanlslav J. F. , Easwaran C. V. , Kokal S. L.
Published: December 2007

A mathematical model is presented that describes the effect of heat losses on pressure behavior in falloff testing of steam-injection wells. A general solution is presented in the form of type curves (with the heat-loss factor as a parameter), along with the analytical solutions for the asymptotic cases. A new method of falloff data analysis also is proposed.