bluuebunny/crossref_metadata_2025 huggingface dataset:
The Fracmeter: A New Numerical Method to Evaluate the State of Stress and the Elastic Properties of Rocks
Authors: Charlez P. , Saleh K. , Despax D.
Published: December 2007

The fracmeter is a straddle inflatable packer with a spacing fitted with radial displacement transducers. When a hydraulic fracture is created it can be shown that the displacement field around the wellbore becomes anisotropic with a maximum value perpendicular to the fracture plane.

The multiplication of the number of equations relating the radial displacement of the borehole and the pressure makes it possible by an appropriate inverse method to determine with a single test the two horizontal geostatic stresses, the elastic constants of the rock and the fracture azimuth.
Gas Injection in the Eastern Fault Block of the Thistle Field
Authors: Laidlaw W. , Bayat M. G. , Tehrani A. D. H.
Published: December 2007

Gas injection commenced in the Thistle field early in 1980, to conserve excess produced gas. By April 1984, 4.3 billion scf [122 × 106 m3] of gas had been injected in a single down-flank well. Analysis of the reservoir performance indicates that about 543 Mstb [86 × 103 m3] of additional oil was produced as a direct result of the gas injected. The net gas used, allowing for produced injected gas and additional fuel gas for compression was 3.2 bscf [90 × 106 m3], resulting in a gas-to-recovered-oil ratio of 5.8 Mscf/stb [1040 m3/m3].
Hydrocarbon Production from the Devonian Shale in Letcher and Knott Counties, Eastern Kentucky
Authors: Kemper J. R. , Frankie W. T. , Moody J. R. , Johnston I. M.
Published: December 2007

The Kentucky Geological Survey (KGS) at the University of Kentucky is conducting a research project funded by the Gas Research Institute (GRI) to study hydrocarbon production from the Devonian shale in eastern Kentucky. The primary objectives of this project are to develop an understanding of the relationship between local geology and hydrocarbon production from the Devonian shale, to create a comprehensive Devonian shale data base of well information, and to prepare an oil and gas report for each county in the study area. Project data have been compiled from the KGS oil and gas well record files, the GRI Eastern Gas Data System (EGDS), files from the U.S. Department of Energy (DOE), and records from cooperating oil and gas companies operating within the study area.

Gamma-ray logs were found to be the most valid means of identifying the stratigraphic units within the Devonian shale. Temperature logs are used to locate gas shows in order to determine which interval to stimulate. The combined use of the temperature log to find the gas shows, and the gamma-ray log to identify which stratigraphic unit the gas is coming from, is an invaluable method for determining the treatment interval.

The two most common methods of stimulating production in Letcher and Knott Counties are explosive shooting and hydraulic fracturing. Comparison of the initial potentials both before and after treatment indicates that hydraulic fracturing is preferable to borehole shooting for improving production in the Devonian shale.

Data compilation in Letcher and Knott Counties is complete. An extensive data base of information on the 1,412 Devonian shale wells in Letcher and Knott Counties has been compiled. Using this information, detailed stratigraphic cross sections within the Devonian-Mississippian shale sequence have been constructed, as well as structure, isopach, and isopotential maps.

Analysis of the maps and cross sections suggest two relationships. There appears to be a direct relationship between areas of high Devonian shale initial open-flow potential and 1) the location of shallower hydrocarbon production, and 2) the location of linear features determined from LANDSAT imagery.

The preliminary results of this study provide the petroleum industry with valuable guidelines for the future exploration of natural gas in the Devonian shales of eastern Kentucky.
Dimensionless IPR Curves for Predicting the Performance of Fractured Gas Wells
Authors: Chase R. W. , Williams M. A. T.
Published: December 2007

Dimansionlees IPR curves have been developed for predicting the performance of fractured gas wells. The equation for pressure drawn-down in a gas reservoir producing under pseudo-steady state conditions was solved utilizing an equation which related fracture length and skin factor to wellbore radius, yielding two distinct dirrensionless IPR curves. Fractured wells with zero and negative skin factors exhibit the sane dirrensionless IPR behavior reported by Mishra and Caudle for unfractured gas wells. Fractured wells having a positive skin factor, while less commonly observed in actual field practice, yield a linear dirrensionless IPR curve. The resulting curves provide the engineer with a method for predicting gas well deliverability from a single stabilized flow test and shutin, thus eliminating the need for multi-point tests.
Long-Term Mothballing of Production Facilities in a Marine Environment
Authors: Ohaly M. , Moench C. J.
Published: December 2007

ARAMCO has several offshore and onshore producing plants that will need to be preserved in a marine environment for several years. This paper is a synopsis of the information we have gathered for this task and of the methods we are using to mothball these plants.
A Comparison of Two Approaches to Compositional and Black Oil Simulation
Authors: Wong T. W. , Firoozabadi A. , Nutakki R. , Aziz K.
Published: December 2007

This paper examines the relative strengths and weaknesses of solving a fully compositional isothermal three phase numerical simulator by two fundamentally different approaches. One of the methods considered is based on the standard Newton-Raphson procedure where the partial derivatives for all the pertinent equations are written with respect to a selected set of primary variables in a Jacobian matrix. This model can be solved fully implicitly as Coats did, or implicitly for pressure and explicitly for saturation and composition (IMPEM) as Fussell and Fussell or Young and Stephenson did. The alternative method, first proposed by Acs et al., is based on a volume balance where in each simulator block, the pore volumes are equated with the fluid volumes. As originally proposed, this method was also an IMPEM one, but Watts later extended it to include a sequential step implicit in saturation. As yet, no computational results have been published for this volume balance method.

The Young and Stephenson model is compared with the IMPEM method of Acs et al. as well as the sequential method of Watts. The main area of comparison is the relative ease or difficulty with which each simulator handles various compositional problems. The advantages and disadvantages of using either method under different circumstances are discussed. As well, the performance of these simulators in their corresponding black oil forms is compared.

Both models can be run using either the Peng Robinson, Soave-Redlich-Kwong, or Schmidt-Wenzel equations of state. All the derivatives needed in both models can be solved explicitly from analytical expressions that have been derived from these equations of state.
A Thermal Simulator for Naturally Fractured Reservoirs
Authors: Chen W. H. , Wasserman M. L. , Fitzmorris R. E.
Published: December 2007

Because of the relatively heavy oil (8 − 12° API) encountered in many naturally fractured reservoirs, thermal recovery processes could be viable recovery techniques to produce oil from these reservoirs. To facilitate the simulation of these processes, a simulator to model thermal effects in naturally fractured reservoirs has been developed. The model uses the double porosity concept and is three dimensional, three phase, and compositional. It allows the rock matrix block to be subdivided into a two-dimensional (r−z) grid block in order to study effects of gravity, capillary pressure, and mass and energy transfer between fractures and matrix blocks. The simulator is fully implicit and has a coupled wellbore mathmatical formulation, and simultaneously solves the unknowns for fractures and matrix blocks. An efficient solution procedure is implemented so that the cost of modelling naturally fractured reservoirs is not significantly greater than the cost of conventional single porosity thermal simulation.

An example, steam injection into a five-spot pattern, is included to illustrate the significant effects of physical properties and model construction. Oil recovery predictions are sensitive to capillary pressure values, the number of cells used to divide the matrix block, and the size of the matrix blocks.
Computing Absolute Transmissibility in the Presence of Fine-Scale Heterogeneity
Authors: White C. D. , Horne R. N.
Published: December 2007

This paper presents an algorithm to compute transmissibility when there is permeability heterogeneity and anisotropy at the subgrid scale. The need for a tensor representation of macroscopic transmissibility in order to scale properly the effects of microscale permeability variations is demonstrated. Methods for computing tensor transmissibility and the use of tensor transmissibility in reservoir simulation are described. The proposed method is applicable even when the variance of permeability is large and the principal directions of the transmissibility tensor are not aligned with the coordinate axes. Examples demonstrate that the general tensor scaling procedure can give accurate, efficient production estimates on a coarse grid.
Pseudofunctions in Formations Containing Discontinuous Shales: A Numerical Study
Authors: Davies B. J. , Haldorsen H. H.
Published: December 2007

Discontinuous shale-bodies are one of the commonest forms of heterogeneity in productive formations, and may have a significant effect on the response of a field to waterflooding or other oil-recovery operations. The problem of describing these shale-bodies in a multiphase simulation model may be addressed by applying stochastic modelling and pseudofunction technology. The description of shale-body effects at the coarse-grid scale is affected by dynamicity and representative elementary volume considerations.
Least-Squares Finite Elements for Convective Transport Problems
Authors: Carey G. F. , Jiang B. N.
Published: December 2007

Convective transport problems have been difficult to treat with Galerkin-type finite-element methods, and this has led to upwind Petrov-Galerkin and Taylor-Galerkin variants of the method. Here, we develop a novel approach to the problem based on a least-squares formulation for first-order systems. The method is shown to lead to a discrete problem similar to that of the Taylor-Galerkin approach and to produce excellent results for purely convective transport (infinite Peclet number) in one dimension. The further extension of the method to nonlinear problems is described and test results for a model problem given.
Simulation of Flow in Naturally Fractured Reservoirs
Authors: Douglas J. , Leme P.J. Paes , Arbogast T. , Schmitt T.
Published: December 2007

This paper describes two models for simulating flow in naturally fractured petroleum reservoirs, one for single phase flow of a fluid of constant compressibility, and the other for two-phase, incompressible, immiscible flow. Both models are based on the dual porosity concept, in each model the flow in an individual matrix block is simulated using the standard equations describing flow in unfractured media, and the matrix/fracture interaction is based on the imposition of proper boundary conditions on the surface of the block. The models are presented in an easily parallelizable form.
Parallel Iterative Linear Equation Solvers: An Investigation of Domain Decomposition Algorithms for Reservoir Simulation
Authors: Killough J. E. , Wheeler M. F.
Published: December 2007

The use of parallel iterative techniques for the linear equations associated with reservoir simulation was investigated. A technique is described in which a lower dimensional problem is used as a correction to the preconditioned generalized conjugate residual method with the domain decomposition technique as the overall preconditioner. For the cases investigated the method proved to be both robust and efficient.

Three example matrices, including a highly heterogeneous example, an example from the SPE/SIAM comparative solution project, and a nonsymmetric IMPES reservoir simulation example, are presented to validate the method. Several comparisons are made with other well-known preconditioners including incomplete LU and reduced system/incomplete LU factorizations. For the examples considered the domain decomposition technique was the most efficient in a nonparallel environment; in a parallel computational environment the algorithm was several times more efficient than the other techniques. An analysis was made concerning both vector and parallel computational aspects of the domain decomposition method. Numerical experiments showed that the effect of the number of domains on the convergence rate is small. Corrections using a lower dimensional problem, known as line corrections, were found to be necessary for the rapid convergence of the method. Finally, the three dimensional domain decomposition algorithm was efficiently implemented in parallel computational environments using multitasking and microtasking on both the CRAY X/MP 48 and IBM 3090/400 four-way parallel supercomputers.
Equation of State Compositional Modeling on Vector Processors
Authors: Young L. C.
Published: December 2007

Previously, large simulation problems have not been feasible with equation of state (EOS) compositional models. This paper describes an approach for efficient EOS calculations. Tests of a simulator based on the approach, show that large problems can now be solved. For example, a problem composed of 9-components, 20,000 grid points, and 1,000 time steps can be solved in approximately 40 minutes of CPU time on a Cray X-MP.
Efficient Fluid Behavior Computations in a Sequential Compositional Reservoir Simulator
Authors: Subramanian G. , Trangenstein J. A. , Mochizuki S. , Shen E. l-C.
Published: December 2007

A compositional reservoir simulator using a sequential formulation of the fluid flow and phase equilibrium equations requires that the phase equilibrium and associated derivatives of the dependent phase equilibrium variables with respect to the pressure and moles of individual components be computed every time step for all the grid blocks in the system. The phase equilibrium calculations are computation intensive, since they solve a nonlinear system of equations and are thus iterative in nature.

This paper describes techniques for implementing the phase equilibrium and the associated derivative calculations in a sequential compositional reservoir simulator designed for large reservoir models. These techniques use strip mining and optimal strategies for treating gridblocks at similar mathematical convergence or physical states and have been very successful in reducing computation times and memory requirements for iterative computations in the simulator, both on the CRAY and IBM computers.

The derivative calculations are unified in that a single matrix can be used to generate derivatives of phase equilibrium variables with respect to any of the dependent variables used in the flow/conservation steps used in the simulator. Results are presented to illustrate various cases.
The Use of Vectorization and Parallel Processing for Reservoir Simulation
Authors: Chien M. C. H. , Wasserman M. L. , Yardumian H. E. , Chung E. Y. , Nguyen T. , Larson J.
Published: December 2007

A general purpose reservoir simulator was developed as a vehicle to investigate vectorization and parallel processing on the Cray XMP/48. The simulator can model black oil, compositional and steam injection processes. It includes both fully implicit and IMPES formulations. Microtasking is used for parallel processing in order to maintain the portability of the code.

The simulator calculations other than linear equation solution were structured to facilitate vectorization and parallel processing. Several issues concerning parallel processing are discussed. These include task granularity, load balance, synchronization, memory contention, and balance between vectorization and arallel processing.

Based on three test problems, the speedup of the calculations due to vectorization ranges from 5.3 to 10. The speedup can be augmented by as much as 3.3 times through parallel processing. The scheme proposed here is general enough to be applicable to other vector and parallel processing computers.
A General Purpose Chemical Flood Simulator
Authors: Scott T. , Sharpe S. R. , Sorbie K. S. , Clifford P. J. , Roberts L. J. , Foulser R. W. S. , Oakes J. A.
Published: December 2007

A new advanced and versatile chemical flood simulator has been developed for modelling polymer and surfactant oil recovery processes. The simulator takes into account many important fluid properties and includes a sophisticated treatment of phase behaviour. The modelling of temperature effects forms an integral part of the program, allowing for heat transfer between fluids and reservoir formation. Other important features include non-Newtonian rheology, chemical reaction and component degradation, adsorption of components, velocity dispersion effects, and fluid and rock compressibility.

The scope of the simulator is illustrated by application to several representative polymer and surfactant examples. These give an overview of the extensive range of problems which can be handled by the program including studies at the field and laboratory scales.
A Framework for Multiphase Nonisothermal Fluid Flow in a Deforming Heavy Oil Reservoir
Authors: Tortike W. S. , Ali S. M. Farouq
Published: December 2007

The problem of multiphase (oil, water, gas), non-iso-thermal fluid flow in a heavy oil reservoir is of great interest in thermal recovery operations, especially steam injection. The much more complex problem of simultaneous stress-strain calculations in the reservoir and adjacent media, and reservoir compaction or dilation is of great importance in regions of Canada, Venezuela and the U.S.A. Such an extended problem is the theme for this paper.

The subject problem is being solved by the finite element method (FEM) for a three dimensional system. Flow of oil, water and a gaseous phase including steam, with the flow of heat, and simultaneous reservoir deformation is expressed by the appropriate partial differential equations (PDEs). The flow equations are formulated by the Petrov-Galerkin technique applied to the weighted residual method, and the stress-strain equations are solved by standard finite element techniques.

The simulator is being developed on the CDC Cyber 205 vector processor, which provides the high computational speeds needed for such a complex problem. The computational effort required by the finite element method has limited its wider use in reservoir simulation, where finite difference methods are the norm.
Borehole Stresses: Plasticity and the Drilled Hole Effect
Authors: Mitchell R. F. , Goodman M. A. , Wood E. T.
Published: December 2007

Borehole stresses and deformations can be the cause of numerous high cost drilling, completion, and production problems, including:

Drill string and casing sticking through borehole contraction, Gas migration due to ineffective sealing between casing, cement, and borehole wall, Breakdown and possible mobilization of formation material leading to impaired productivity/injection, Borehole destabilization with possible sand production, and Overestimation of porosity from logs due to dilatation around the borehole.

This paper presents an elastic-plastic model that predicts borehole movement and quantifies the effects of yield around the borehole as the hole is drilled. Results are reduced to a family of dimensionless curves incorporating key variables of mud weight, rock properties, hole geometry, and in-situ stresses. Borehole unloading during drilling and also reloading during cementing and completion operations can be evaluated. Qualitative comparisons to case histories are provided to demonstrate the borehole movement relationship and to explain behavior observed in specific wells.
An Analysis of Discrepancies Between Gyro Surveys
Authors: Thorp M.
Published: December 2007

Several gyro survey systems have been introduced recently with claims of high accuracy. Only limited data have been published in support of the claims, and it has generally been in unchallenging wells (low angle, latitude, temperature, depth). This paper presents data from 12 Ninian Field wells with hole angles of up to 65°, depths to 18500′ and a latitude of 61°N.

Two companies surveyed each well. The bottom line and claimed accuracy of each survey is summarised. Horizontal differences between the tools vary from less than one foot to over 200 feet at T.D. A statistical analysis is presented comparing observed and expected discrepancies. Chi-squared and Student's ‘t’ tests are applied to the data and suggest that neither tool suffers from a systematic error relative to the other; the spread of errors does, however, indicate that the differences are statistically surprising.

Without a benchmark survey one cannot prove that either system is wrong. What is done instead is to derive working accuracy values based on which the observed discrepancies are no longer surprising.

In five of the wells an inertial navigation tool was run in the 133/8″ casing in addition to the two other systems which were run at T.D. The data at equivalent depths is presented and a similar statistical analysis is applied.
UL's Third-Party Approach to Intrinsic Safety Testing
Authors: Bartkus A. A.
Published: December 2007

The use of intrinsically safe instrumentation and wiring reduces the potential of fire and explosion hazards due to ignition by electrical arcs or high temperatures of flammable gas mixtures that may be released during the drilling operation. To determine compliance with national or international standards, the inspection authorities usually require that such equipment be third-party listed, approved or certified.

Underwriters Laboratories Inc. (UL) third-party evaluation of intrinsically safe circuits and instrumentation for use on drilling rigs is described. Examples are given of the types of instrumentation available to monitor the drilling process, designation of the hazardous locations, and how the instruments are constructed to be intrinsically safe – meet the requirements in the ANSI/UL/NFPA 4913 standard.

The principles of the intrinsic safety method of protection are explained and shortcut approaches for evaluation and design are discussed. The electrical and thermal energy available in the intrinsically safe instruments and circuits is so low that under normal operation, or fault conditions, they are not capable of causing ignition of the flammable mixture. The intrinsically safe circuits are separated from any higher energy circuits both inside the instrument and during field installation.

Additionally, the UL investigatory procedures for intrinsically safe instrumentation to international and foreign national standards are reviewed, along with the highlights of the recently developed UL Certificate program aimed at facilitating acceptance of such products overseas. The information contained in a certificate is examined.
A Contractor's History of Drillstring Failures in the Anadarko Basin
Authors: Hampton S. D.
Published: December 2007

Helmerich & Payne International Drilling Co. has developed a data base of drill string failures experienced in the Anadarko Basin over a two year period. The analysis of this data has led to some operational changes in an effort to minimize drill string problems. This paper discusses the drill string failures experienced as well as the courses of action taken in an effort to reduce future failures.

Significant conclusions have been drawn from both the drill collar failures as well as the drill pipe failures. The drill collar failure analysis shows that a minimum bending stength ratio of 2.4 is recommended to avoid drill collar connection problems in the Anadarko Basin. Analysis of the drill pipe failures revealed that 43% of the failures occurred within the first 15 joints above the bottom hole assembly· As a result, H & P has increased the use of heavy walled drill pipe above the bottom hole assembly.
A Potassium-Base Derivative of Humic Acid Proves Effective in Minimizing Wellbore Enlargement in the Ventura Basin
Authors: Pruett J. O.
Published: December 2007

A potassium-base derivative of humic acid has been designed and developed for water-base drilling fluids. The product has proven successful as a rheology control agent in both dispersed and non-dispersed potassium muds.

This organopotassium complex additive:

is an effective deflocculant, provides source of potassium ion for inhibition, can be used in low/high pH, fresh/seawater muds.

In addition, the 3 mud system formulated with OPC has favorable aquatic toxicity levels when compared to alternative potassium-base mud systems.

Initially OPC was used to replace the traditional lignites and lignosulfonates in KOH/lignite and KOH/lignosulfonate systems. After being laboratory tested for thinning ability and inhibitive characteristics, OPC was field tested. Field application on wells in the Ventura Basin resulted in improved hole size and excellent primary cement bond logs. Compared to offset wells drilled in the area, combined drilling and cementing costs were reduced.

This paper covers the development and initial field application of OPC. Both the theory behind its design as well as system formulation are included.
Protective Colloid System Improves Solids Removal Efficiency, Drilling Fluid Stability, and Drilling Performance
Authors: Clark D. E. , Daniel S.
Published: December 2007

The utilization of a partially hydrolyzed polyacrylamide (PHPA) as a protective colloid in over 300 wells on the Louisiana and Texas Gulf Coast has shown evidence that this type of fluid not only stabilizes well bores, but has many other advantages which increase drilling performance and reduce overall drilling costs. The use of this system has demonstrated high rates of penetration, longer bit life, less stuck pipe and less mud to dispose of than other water base systems.

The observed decrease in drill cutting dispersion exhibited by this fluid results in increased solids removal efficiency by the solids control equipment. The resulting low colloid content drilling fluid, in combination with the PHPA, favorably affects all drilling parameters.

The rheological properties exhibited indicates minimal viscosity at the bit, resulting in higher rates of penetration. Increased hole cleaning ability is observed, which also contributes to decreased torque, drag, and stuck pipe.

The low colloid solids content/PHPA combination results in a thin, slick filter cake. Such a filter cake has minimized torque, drag, and stuck pipe.

The utilization of a dependable water meter, combined with a set of simplified equations, allows the solids removal efficiency and polymer additions to be calculated on a daily basis. Comparisons between numerous offset wells has demonstrated improved solids removal efficiency, drilling fluid stability and drilling performance.
Lost Circulation: A Solution Based on the Problem
Authors: Gockel J. F. , Gockel C. E. , Brinemann M.
Published: December 2007

Lost circulation requiring positive treatment can best be solved by using materials similar in structure to the formation involved. Use of a vitrified, mineral-based granular material is best suited to this purpose because of its wide range of applicability and the unique features which this type of processing produces.
Case History of a 22,000-ft Deepwater Wildcat
Authors: Gordy C. A. , Combes J. F. , Childers M. A.
Published: December 2007

Chevron U.S.A. Inc. recently drilled a 22,000 ft., deep-water wildcat in the Eastern Gulf of Mexico with Odeco's Ocean Rover. The Destin Dome Block 422 well, in 600 ft. of water, set three world records for wells drilled from floating vessels.

A number of operational and technical challenges resulted from this combination of drilled depth and water depth. These included casing design, subsea equipment design, rig design and selection, drill string design and unique logistical requirements.

This paper presents a case history of the well and emphasizes how joint planning and good operator/contractor cooperation can contribute to operational success. Results will show that a conservative, methodical approach with careful planning yielded a near trouble free operation on a high cost, critical well.
Incentive-Type Contract Improves Rig Performance
Authors: Cahuzac J. P.
Published: December 2007

Incentive type drilling, uncommon in the drilling industry during the boom period several years ago, is currently generating renewed interest since it creates more motivation for improvement in rig performance which will result in reduced well costs. There are several different kinds of incentive type contracts in use today. Footage and turnkey contracts are the best known and are popular in many areas. When these kinds are not in the operator's and contractor's best interests, other types of contracts can still have a positive impact on the operations. Incentive Dayrate is one such contract. By making the operator's and contractor's objectives match, it creates a new team spirit between all the parties involved and allows the contractor to provide a better quality service. SEDCO FOREX experience shows that well operations are completed safely and more efficiently.
Driveability Performance Analysis of Threaded Connectors for Conductor Casing in Offshore Drilling
Authors: Milberger L. J.
Published: December 2007

This paper introduces a unique new system to quantify the driveability and strength of mechanical connectors for conductor casing that are subjected to the action of a pile driving hammer. The rating criteria, presented in terms of allowable pipe stress, are supported by extensive pile driving tests in which instruments located above and below the connectors measured the force-vs.-time and velocity-vs.-time characteristics of the stress wave traveling through the joint. Material qualification tests are also presented to demonstrate the desirable properties of materials suitable for driveable connectors.
Hang Casing Right and Reduce Failures
Authors: O’Brien T. B.
Published: December 2007

At least 25 years ago an API study group in the Mid Continent recommended casing should be landed as cemented. API RP 5C 1 recommends the same thing today. Numerous papers in the interim recommend the same thing with some showing the need for added tension. Yet many operators/contractors consider slacking off 20-50% of pipe weight to be standard practice. Numerous casing failures are traceable to the practice of slacking off weight. Proper hanging practice can eliminate most of such failure.
Application of Side-Force Analysis and MWD to Reduce Drilling Costs
Authors: Whitten R. G.
Published: December 2007

This paper describes a method by which the accumulative effects of borehole severity, interpreted lithology from measurement-while-drilling (MWD) gamma ray intensity, and bottom hole assembly (BHA) geometry may be combined to predict the probability of sticking during the drilling process.
Drilling Engineering Considerations in Designing a Shallow, Horizontal Well at Norman Wells, N.W.T., Canada
Authors: Markle R. D.
Published: December 2007

Unique engineering problems are encountered when designing shallow, long displacement horizontal wells. For a recent well of this description drilled in a remote northern location, the major engineering tasks identified in well planning were: 1) manage the impact of wellbore torque and drag to meet drilling objectives, 2) produce a high quality cemented wellbore capable of long term oil production, and 3) obtain high quality geological information to better define reservoir characteristics at the reef boundaries. This paper discusses how these specific issues were engineered for the drilling program.
Lost Circulation Challenges: Drilling Thick Carbonate Gas Reservoir, Natuna D-Alpha Block
Authors: Bell R. J. , Davis J. M.
Published: December 2007

The L-Structure in the Natuna D-Alpha Block of the East Natuna Basin is located in the Natuna Sea in Indonesian waters, northwest of Kalimantan. The structure is a large structural stratigraphic hydrocarbon trap and is unique in areal extent and reservoir thickness among the various carbonate traps which are present in many southeast Asian basins. The porous reef complex (Terumbu formation) has a fairly homogeneous gas column 5,200 feet thick with CO2 content averaging 72%. The purpose of this report is to summarize the exploration drilling problems in the reservoir relating to severe lost circulation occurrences and to explain the steps which have been taken to alleviate these problems.

The thick Terumbu reservoir is a fractured, vuggy limestone. Furthermore, the long gas column in the reservoir presents a pore pressure profile which ranges from abnormally high in the top, down to a fresh water gradient in the bottom. The above factors compound the task of dealing with lost circulation and lead to additional drilling problems. Much progress has been made in reducing the severity of lost circulation and lessening its effects on drilling operations. Careful casing seat selection, improved drilling practices, strict control of drilling mud properties and use of lost circulation material in the mud while drilling have been major contributors to successful penetration of the entire reservoir.
Bit Performance and Selection: A Novel Approach
Authors: Farrelly M. , Rabia H.
Published: December 2007

Much research has been dedicated to a better understanding of the factors involved in the drilling process. Equations are becoming more and more complex and require numerous empirically derived constants to be effective. An equation is presented here that relies upon the well-proven specific energy analysis of rock cutting. The equation used is simple, easy to apply to field drilling data studies and can easily be correlated from well to well. Although containing one empirical constant the authors have found this to be of minor importance.

The specific energy equation is applied to three wells in the North Sea, where detailed drilling parameter data were available. Specific energy is shown to indicate lithology changes and correct bit selections based on drilling performance. The specific energy approach to bit selection is not intended to be used entirely on its own, but in conjunction with more normal bit selection aids, such as the study of past offset bit records and cost per foot.
A Comparative Analysis of Efficiency and Horsepower Between Progressing Cavity Pumps and Plunger Pumps
Authors: Saveth K. J. , Klein S. T. , Fisher K. B.
Published: December 2007

In selecting production equipment for a given well, the highest efficiency and the lowest required horsepower is the ideal situation. The progressing cavity pumping system is more efficient and requires less horsepower than the plunger pumping system at 150 BPD and 500 BPD from 2000 feet and 4000 feet respectively.
Jarring Effects on Retrievable Gas Lift Equipment
Authors: Barker L. D. , Hathcock L. A.
Published: December 2007

Gas lift equipment problems such as inconsistent valve performance, leaking valves, and bent/broken latches occasionally occur. To quantify the effects of jarring on valve opening pressure, leakage, and latch deflection, simulated field testing was performed on 1 in. pressure operated gas lift valves, BK-2 style latches, and associated wireline tools. The testing was done in 2-7/8 in. and in. side pocket injection mandrels positioned both vertically and at a 45° angle.

Jar-down testing simulated the setting of a valve in the mandrel pocket. During the jarring sequence, new thoroughly aged valves exhibited fairly consistent opening pressures (average variance 0.7%), but usually leaked as the pressure was bled off. Used valves that had been disassembled, cleaned, and functionally tested exhibited large opening pressure changes and also leaked significantly during jarring.

Jar-up testing simulated the retrieval of a valve lodged in a mandrel pocket. Orienting kickover tools from two manufacturers were used in a 412 in. mandrel. New BK-2 style latches made of 17-4 PH material deflected more than 0.200 in. (5.1 mm), but exhibited no significant damage.
The Effect of Perforating on the Performance of Shale-Laminated and Crossbedded Formations
Authors: Ichara M. J. , Cannon D. E.
Published: December 2007

The productivity of a completed well depends, to some extent, on the internal structure of the formation. This internal structure includes shale laminations and current beds of crossbedded units. In order to drill to "target" formations, hundreds of feet of laminated and crossbedded formations are traversed. Optimal shot density distribution is essential for completing these laminated formations. Too low a shot density limits production; too high a shot density wastes money and can cause casing damage. Tailoring the perforating to the minimum number of shots for optimum flow will improve the well's economics.

This study used a general-purpose finite-element program to simulate perforated, shale-laminated, and crossbedded formations.

A field example was used to investigate the effect of perforating on the performance of shale-laminated formations. The results show that 1) at high shot density, the performance of a laminated formation is practically independent of perforation location; 2) at low shot density, shale/sand distribution controls the performance of shale-laminated formations; 3) the performance of crossbedded formations is not a function of the dip angle of the foreset laminae but is a strong function of perforation length, with the perforation intercepting the laminae.

A shale distribution index has been defined and correlated with the productivity ratio of laminated formations. This correlation can be generated for a key well in the reservoir and the results can be used for optimal shot density selection for completion of the key well and other wells in the same reservoir.

A summary of recommendations for completing various formations, based on the results of this study and those of other investigators, is presented.
Application of Primary Cementing Principles, Rocky Mountains and Texas
Authors: Smink D. E. , Kundert D. P. , Vacca H. L.
Published: December 2007

A review of 23 primary cementing jobs performed over an 11-year period in four states has shown that success is improved When attention is directed to low-cost means of improving displacement of drilling muds by cement slurries. The most important factors appear to be placement of centralizers and scratches, conditioning of the drilling mud, and pipe movement (reciprocation) while conditioning mud and while placing cement. Confidence gained in the use of these methods has resulted in a job technique wherein the top cementing plug is pumped down with 10% acetic acid or other desired perforating fluid followed by 2% KCl water. This technique permits lower cost completions.

The theory and application of cement bond logging are reviewed. Five example CBL-VDL logs are presented and discussed. Several examples are shown under applied surface pressure conditions. An example of a CBL-VDL log of an offset well where the principles of primary cementing were not observed is shown for comparison.
Curable Resin-Coated Sand Controls Proppant Flowback
Authors: Pope C. D. , Wiles T. J. , Pierce B. R.
Published: December 2007

A study of fracture stimulations in two South Texas oil fields indicated that proppant flowback was a major problem. This paper examines thirty-four stimulations that used 100% sand as the proppant and thirty-five stimulations that used a tail-in of resin coated sand.

In the Big Wells Field, thirty-one wells have been fracture stimulated using 100% sand as the proppant. These wells averaged 1.25 failures per well per year. In the North Government Wells Field, three wells have been fracture stimulated using 100% sand as the proppant. These wells averaged 5.40 failures per well per year.

In order to reduce the incidence of proppant flowback while maintaining a high sand concentration, curable resin coated sand was substituted for the final 10-20% of the recommended amount of sand in the fracture stimulation. Once this resin coated sand is pumped into the fracture, it chemically bonds together to form a barrier against proppant flowback. In the Big Wells Field, thirty-one wells have been fracture stimulated using a tail-in of resin coated sand. These wells averaged 0.19 failures per well per year. In the North Government Wells Field, four wells have been fracture stimulated using a tail-in of resin coated sand. These wells have averaged 2.43 failures per well per year.

Characteristics of wells with proppant flowback were examined with respect to bottomhole pressure, waterflood response, and acid stimulation. A comparison was made between wells stimulated with 100% sand and wells stimulated with a tail-in of resin coated sand using decline curves and post fracture stimulation bottomhole pressure buildups.

Based on the results of these sixty-nine fracture stimulations, it can be concluded that a tail-in of resin coated sand is an effective method of controlling proppant flowback following fracture stimulation.
Temperature Data from Cement Interval Extremities Give Reduced WOC Time
Authors: Sykes R. L. , Stehle D. E. , Venditto J. J.
Published: December 2007

A more realistic and better engineered cement slurry can be designed when bottomhole and top-of-cement (TOC) temperatures are known. These data can be obtained by running temperature recorders in the drill string during the clean-up trip, with one recorder at the bottom (TD) and one at the anticipated TOC. This configuration shows the actual temperature changes that the cement will experience. By noting the circulating rates during the temperature gauge run, the time to reach these temperature extremes can be calculated.

Laboratory tests can be modified to reflect these temperature extremes and heat-up rates to yield a more realistic cement design. The use of this modified testing procedure can result in lesser concentrations of retarder, better early compressive strengths at the TOC, and reduced WOC (waiting-on-cement) time.

This paper presents details of procedures used to (1) obtain temperature readings, (2) calculate heat-up rates for cement testing, (3) test optimum slurries, and (A) conduct cement jobs utilizing the optimized slurry.

Laboratory test data are presented showing (1) reduced retarder concentrations obtained by utilizing this modified test schedule, (2) better early compressive strengths at the top-of-cement, and (3) comparison of modified test results to standard API test results.

Field results showing WOC times and bond logs are presented.
Supervisory Control of Beam Pumping Wells
Authors: Dunham C. L.
Published: December 2007

Close monitoring and control can greatly improve the effectiveness and economy of beam pumping operations, especially in oil fields with large numbers of wells.

Shell Oil Company has developed an oil-field supervisory control system for centralized computer monitoring and control of beam pumping wells equipped with microprocessor-based pump-off controllers.

This paper reviews the history of computerized beam pump monitoring and control in Shell, describes the capabilities of Shell's current system for supervisory control of beam pumping wells, discusses the operating and maintenance requirements for such a system to be successful, and reviews the benefits which are often realized.
Real Time Decision-Making through Use of a Log/Log Plot During a Frac Job
Authors: Jopling M. W. , Ketcher N. W.
Published: December 2007

Since the publication of the paper by Kenneth G. Nolte and Michael B. Smith, "Interpretation of Fracturing Pressures" (September, 1981, JPT), more attention has been given to the meaning of pressure changes during fracturing treatments. Initially, log/log plots were made by hand, which usually did not allow sufficient time to make decisions affecting the job. In recent years, the major stimulation companies have introduced, into the field, treatment monitoring vans which have the capability to make real-time log/log plots of net pressure above closure vs. time. With the continuous plotter, the field supervisor can observe slope changes indicating lateral extension, height growth, excessive fluid leak-off, width growth or screenout conditions and have tine to make changes in job design as the situation requires.

In this paper, an example is given in which a screenout was avoided through use of the real-time log/log plot (Nolte-Smith plot). The log/log plot began indicating a screenout before the surface treating pressure had significantly increased. This was due to a higher density sand concentration being pumped down the tubing.

The ability of the treatment monitoring van (TMV) to sample data every 2 seconds and to display the data (both measured and calculated) every 10 seconds on a TV monitor, allows the field supervisor to visually follow the progress of the job. Western's TMV displays the data in 4 formats: TV monitors (2), x-y bed plotter, digital printout, and continuous strip chart. The TV monitors may be used to display total job and log/log plot, segmented job and total job, one parameter and total job or any combination as required by the field supervisor or engineer. The raw data, stored on two discs, is available for post-frac analysis if needed.

Although the Nolte-Smith1 technique for predicting screenouts requires a "dead string" pressure input, it is possible, by careful use, to utilize the computer to measure, record, calculate and display data for use as an on-site decision-making tool.
Combining Transient Rate and Pressure Data with Production Logging for Enhanced Well Test Analysis
Authors: Bingle C. F.
Published: December 2007

Many gas wells drilled today are completed over 100 ft or more of gross pay interval to maximize deliverability, reserves, and revenue. Formation permeability of these wells is usually very low (less than 1 md). Use of conventional transient pressure analysis to understand formation properties is seldom done because of time (many days or even weeks) needed to acquire correct answers. Knowledge of producing zones and their respective amounts are rarely studied. Such limited knowledge concerning formation properties (permeability, pressure, drive mechanism, etc.) and flow profiles can often lead to poor reservoir management throughout the life of the field and eventually leave many thousands of dollars of reserves behind.

Combining production logging with the transient rate and pressure analysis (TRAP*) allows one to identify the wellbore's flow profile and formation flow properties such as permeability, average reservoir pressure, and skin factor (near wellbore and total skin) in less than one day. Such combination testing can identify flow regime, drive mechanism, coning or fingering problems, unusual pressure or zonal depletion, presence of crossflow, scale, or plugged perforations; all of which if identified in time, can be used positively to maximize production and revenue.

The TRAP technique uses the production logging tool. First, up and down passes over the perforated interval are made prior to the well test to identify the well's flow profile. Production logging passes made at varying flow rates can further be used to identify the reservoir flow behavior, and the associated reason. For the well test part, the TRAP technique incorporates measuring changing rate data with the corresponding pressure data during a buildup, drawdown, or multirate test. Using the principle of superposition (continual integral), it eliminates wellbore storage problems and identifies formation flow properties in a very short time frame.

The TRAP technique is illustrated through the analysis of two deep gas well tests.