bluuebunny/crossref_metadata_2025 huggingface dataset:
Integration of 3D Seismic Data in Reservoir Stochastic Simulations: A Case Study
Authors: Fournier F.
Published: December 2007

Integration of seismic data in stochastic models is a key point for reducing uncertainties on reservoir properties between wells. Stochastic simulations of the average porosity of a reservoir in North Sea, constrained both by well and seismic derived information, are discussed in this paper. Firstly, a non parametric regression based on a multivariate gaussian segmentation is used to calibrate at wells a set of seismic attributes in terms of average porosity. This technique allows to account for multivariate non linear relationships between seismic and porosity information, and also to fully quantify the uncertainties attached to the porosity estimation. Two approaches to account for the seismic derived information in simulations were compared. The first one is based on error cokriging where the seismic porosities constrain the simulations depending on their attached uncertainties. Seismic derived data significantly reduce the dispersions of the simulations, by comparison to the case where only well data participate. In the second approach, a cokriging between well and seismic porosities is used in the simulations. This allows to account for the spatial structure of seismic porosities and to better characterize well porosity spatial structure from its correlation with the dense seismic information. The non parametric regression appears as a way to linearize the seismic information before cokriging with well information.
Integrated 2-D Interpretation of Resistivity Logging Measurements by Inversion Methods
Authors: Eckard M. H. , Mezzatesta A. G. , Strack K. -M.
Published: December 2007

The determination of residual and movable hydrocarbons in oil and gas reservoirs requires that the formation resistivities are accurately estimated. For this purpose the log analyst can use several resistivity measurements with different measuring principles providing varying vertical and radial resolutions. Integrating these measurements into a uniform algorithm mat solves for the formation resistivities can improve the interpretation. Conventional interpretation methods of electromagnetic measurements use approximate and independent techniques for laterolog and induction logging measurements. These techniques do not necessarily provide the same results for the parameter estimates. Using a joint inversion algorithm that simultaneously solves for all measurements provides an earth model consistent with all measurements. In audition, the ability to resolve is enhanced due to the fact that galvanic and induction tools have different response characteristics in conductive or resistive formations. The laterolog is more sensitive to resistive formations; whereas, the induction tool is more sensitive to conductive formations. The combination of both measurements in a joint inversion process, therefore, increases the overall resolution. The inversion technique not only provides the formation parameter results, but gives the log analyst useful statistical information that can be used as quality control.

In contrast with the standard interpretations, which are normally based on a 1-D interpretation, the 2-D inversion can simultaneously solve for a resistivity distribution in the radial and vertical directions. When the resistivity contrast is high, the shoulder bed effects can be very strong. This can be the case if a reservoir is delineated by conductive shales. The different vertical resolutions between deep induction and focussed log measurements appear as an offset between the two curves which could be interpreted as invasion. The 2-D inversion is able to distinguish between shoulder bed and invasion effects and provides more reliable results than a standard 1-D interpretation. Shoulder bed effects may result in underestimating the amount of oil in place if the reservoir is embedded in a conductive formation. The problem of delineating the reservoir and determining the vertical boundaries of the reservoir (and subsequently its thickness, which can be used together with the resistivity to estimate the total amount of hydrocarbon) can be solved using a 2-D inversion.

This work demonstrates how the borehole, invasion and shoulder bed effects influence the data and subsequently the results of a standard interpretation. This is shown using synthetic and real field data.
Use of Pressure Transient Data to Estimate Permeability Variograms
Authors: Yadavalli S. K. , Jones J. R. , Krase L. D. , Yeh N-S. , Roadifer R. D.
Published: December 2007

Variograms for permeability are typically calculated using well log and core measurements, if they are calculated at all. Such procedures are inadequate to estimate variograms for horizontal permeability as they yield almost no information about the short lag structure of the variogram. A well test samples a much larger region of the reservoir than log and core measurements and thus, well test responses are potential sources of data for estimating the horizontal permeability variogram. In Ref. 1, we established the feasibility of calculating this variogram from a single set of well test data. Here we summarize further research on estimating horizontal permeability variograms from well test data. Our major focus in this paper is on improving horizontal variogram estimates by combining responses from tests on a number of different wells. We also address a few issues related to variogram estimation from single well test data. All work presented here is based on simulated well test data using permeability distributions generated with an imposed correlation structure and level of heterogeneity.
Use of Well Test Data in Stochastic Reservoir Modelling
Authors: Holden L. , Madsen R. , Skorstad A. , Jakobsen K. A. , Tjølsen C. B. , Vik S.
Published: December 2007

The aim of the study is to condition stochastic generated realizations on well test data in order to improve simulation of fades and petrophysics in fluvial reservoirs. First we have used the pressure data to estimate the shortest distance from the well to a possible channel boundary and thereby simulate the channel structures. The well test also provides the permeability average in the part of the channel intersected by the well. Together with core/log data and general knowledge of the reservoir this have been used to simulate permeability. These permeability realizations is input to a numerical flow simulator and compared with experimental results of the well test.
Improved Pulsed Neutron Capture Logging With Slim Carbon-Oxygen Tools: Methodology
Authors: Plasek R. E. , Adolph R. A. , Stoller C. , Willis D. J. , Bordon E. E. , Portal M. G.
Published: December 2007

Recently, two new slim through-tubing carbon-oxygen tools were introduced and described in the literature. In addition to carbon-oxygen water-saturation capability, these new instruments can provide, during the same trip, pulsed neutron capture (PNC) measurements (formation sigma, porosity, borehole fluid salinity, etc.). The answers have improved accuracy and precision compared to prior logging instruments. This paper describes the Dual-Burst* PNC measurement scheme for the RST* Reservoir Saturation Tool, as well as the algorithm methodology for determining corrected sigma, porosity, borehole fluid salinity, log quality and other associated outputs. Also documented are database measurements on which the algorithms are based, accuracy benchmarks in industry-standard calibration facilities, and precision (repeatability) comparisons. Log examples are presented.

Diffusion, borehole and lithology effects must be considered when transforming observed quantities such as decay times or near-to-far ratios to actual physical quantities. However, these effects are difficult to account for in direct analytical approaches over the entire range of oilfield conditions. Therefore, a multidimensional dynamic parameterization technique, based on an extensive set of laboratory measurements, has been developed and refined. This technique keeps the order of parameters low, resulting in a well-behaved response both inside and outside the range spanned by the database. The supporting database for each tool includes over 1000 measured points augmented with approximately 400 modeled points spanning different lithologies, porosities, borehole sizes, casing sizes and weights, formation fluid salinities, and borehole fluid salinities typically encountered in the oilfield.

Also reported are the sigma and porosity accuracy benchmark measurements made in the industry-standard calibration facilities (EUROPA facility, Aberdeen, Scotland and API test pits, University of Houston, Houston, Texas, USA). Precision (repeatability) is also compared to prior PNC logging instruments, demonstrating logging speeds typically several times faster for comparable precision.
An Application of Categorical Indicator Geostatistics for Facies Modeling in Sand-Rich Turbidite Systems
Authors: Jordan Douglas L. , Goggin David J.
Published: December 2007

A case study is presented in which a two-stage stochastic modeling approach was employed for modeling heterogeneities in a deep-water Gulf of Mexico field. The hydrocarbon-bearing intervals of this field were deposited as turbidites and exhibit high net sand/gross interval (net/gross) ratios.

In the first stage, a new facies indicator geostatistical method was used to model uncertainties associated with facies maps derived from seismic amplitudes. The concept of pseudo-wells is introduced for capturing geologic features and constraining the stochastic realizations. In the second modeling stage, synthetic stratigraphic columns based on whole core descriptions were used to capture fine-scale heterogeneities in cross-sectional panels. These cross-sections were subjected to flow simulations, yielding scaled-up values of single and two-phase flow parameters. Results from both stages were combined into a full-field 3-D reservoir simulation model.
Integrated Reservoir Description and Flow Performance Evaluation: Glenn Pool Field – Self Unit Study
Authors: Asnul Bahar , Thompson L. G. , Kelkar Mohan
Published: December 2007

This paper presents the study of an integrated approach to reservoir description as a part of the DOE-Class I Projects to improve the oil recovery from a mature oil field. The field selected is the Self Unit of the Glenn Pool Field that covers 160 acres. An integrated reservoir description was constructed which honors the geological, geophysical, and engineering data using geostatistical (stochastic) as well as the deterministic models. The description was validated by comparing the simulated results with static (well log and well core) as well as dynamic (well test) information.

Both stochastic and deterministic models replicate the geological model very well. The deterministic model predicts an optimistic performance, whereas the stochastic model follows the field data much better. The incorporation of geophysical information, taken from tomography surveys, improves the reservoir description when comparing with the observed well test information.

Using the description from each of the models, the flow simulations were conducted to match the historical performance and to predict the future production. Based on the flow simulation and the economic analysis, the plan of recompleting the wells along with an increase in the injection rate is found to be the most feasible solution to improve the performance of the Self Unit. The preliminary results from the implementation of this plan indicate expected results.
Field Development Planning Using Simulated Annealing - Optimal Economic Well Scheduling and Placement
Authors: Beckner B. L. , Song X.
Published: December 2007

A method for optimizing the net present value of a full field development by varying the placement and sequence of production wells is presented. This approach is automated and combines an economics package and Mobil’s in-house simulator, PEGASUS, within a simulated annealing optimization engine. A novel framing of the well placement and scheduling problem as a classic "travelling salesman problem" is required before optimization via simulated annealing can be applied practically. An example of a full field development using this technique shows that nonuniform well spacings are optimal (from an NPV standpoint) when the effects of well interference and variable reservoir properties are considered. Examples of optimizing field NPV with variable well costs also show that non-uniform wells spacings are optimal. Project NPV increases of 25 to 30 million dollars were shown using the optimal, non-uniform development versus reasonable, uniform developments. The ability of this technology to deduce these non-uniform well spacings opens up many potential applications that should materially impact the economic performance of field developments.
Hydraulic Fracture Stimulation of Highly Permeable Formations: The Effect of Critical Fracture Parameters on Oilwell Production and Pressure
Authors: Mathur A. K. , Ning X. , Marcinew R. B. , Ehlig-Economides C. A. , Economides M. J.
Published: December 2007

Hydraulic fracturing of moderate to high-permeability reservoirs with short, highly conductive fractures is a technique often applied to improve well productivity through penetration beyond near wellbore damage. This paper investigates the effect of important fracture parameters (e.g., fracture half-length, fracture conductivity, and fracture-face damage) on the short-term behavior and long-term productivity of the well. The degree and extent of near wellbore damage, in addition to the fracture parameters, are varied in the sensitivity analysis. A case study from the Gulf Coast addresses the effect of these important parameters on the well response.

It is evident the length and conductivity of a created hydraulic fracture have an important effect on the poststimulation performance of a well. Some of these fractures may be damaged. Damage to the proppant-pack has considerable effects, reducing the fracture conductivity. Generally fracture-face damage caused by fluid and polymer leakoff does not significantly alter long-term production, assuming the permanent reduction of absolute permeability is low (less than 90%) and provided the fracture bypasses the radial ldamage zone in the formation. When the fracture face damage is high (greater than 90%), early time well response is significantly impaired by the fracturing fluid cleanup process. This has implications on the timing of poststimulation pressure transient analyses. The modeled behavior and recommendations for the design of such tests are presented.
Quantitative Environmental Risk Analysis
Authors: Klovning Jorunn , Nilsen Espen Fyhn
Published: December 2007

According to regulations relating to implementation and use of risk analysis in the petroleum activities issued by the Norwegian Petroleum Directorate, it is mandatory for an operator on the Norwegian Continental Shelf to establish acceptance criteria for environmental risk in the activities and carry out environmental risk analysis.

This paper presents a ‘new’ method for environmental risk analysis developed by the company. The objective has been to assist the company to meet rules and regulations and to assess and describe the environmental risk in a systematic manner. In the environmental risk analysis the most sensitive biological resource in the affected area is used to assess the environmental damage. The analytical method is based on the methodology for quantitative risk analysis related to loss of life. In addition it incorporates the effect of seasonal fluctuations in the environmental risk evaluations.

The paper is describing the function of the main analytical sequences, exemplified through an analysis of environmental risk related to exploration drilling in an environmental sensitive area on the Norwegian Continental Shelf.
Integrated Horizontal Technology Recovers Attic Gas in West Delta 54 Field
Authors: Schroeder Tom , Mathis D. E. , Doyle B. J. , Wonish Bob
Published: December 2007

In 1994, PANACO, Inc. drilled two horizontal wells in the DP sand of West Delta 54 field - the No. 15 well and the No. 28. The DP gas reservoir had been discovered in 1956 at 3800' TVD, and its vertical wells had already produced 67% of its 28.3 BCF of recoverable gas. The new horizontal wells, designed to maximize recovery, have now produced at a combined rate as high as 25 MMCFPD. The scope of this paper is twofold: Evaluation of return permeability as influenced by a biopolymer mud system, which was used to drill the horizontal sections, andComparison of productivity from two horizontal wellbores of different lengths within the reservoir.

Analysis is based upon initial well tests in addition to the first six-month production history.

This case history may provide guidelines for development of other shallow, high porosity and permeability gas sand reservoirs.
Improved Fractured Reservoir Characterization Using Neural Networks, Geomechanics and 3-D Seismic
Authors: Zellou A. M. , Ouenes A. , Banik A. K.
Published: December 2007

In this paper, a new approach which uses seismic attributes in a quantitative manner to enhance the characterization of fractured reservoirs is presented. The new approach uses the seismic travel time to identify the reservoir structure and the thickness of the fractured producing formation. Using these data, a quantitative geomechanical model is constructed. When comparing the geomechanical models derived from seismic data and mapping methods, it becomes apparent that many structure details may be misrepresented and/or missed when interpolation methods are used for defining reservoir structure. Using a Neural Network and the available well data, the geomechanical model is correlated with the oil production. This model is compared to the seismic amplitude which appears to provide the best indication of fracture intensity in the case of the field studied. Given the seismic data, which are available over the entire reservoir, and the fracture model found by the neural network, the overall reservoir fracture network is predicted.
Splitting Pseudospectral Algorithm for Parallel Simulation of Naturally Fractured Reservoirs
Authors: Luan Zhi-an
Published: December 2007

Improved difference schemes are illustrated for Buckley-Leverret equation. Based on the schemes, new splitting pseudospectral algorithms for some parallel simulations of naturally fractured reservoirs are developed. The component-by-component splitting method effectively splits more complicated multidimensional (or multi-phase,multi-component) problems into simpler one dimensional problems which can be handled by the pseudospectral method or any highly vectorized technique of tridiagonal systems.These algorithms specially suit to accuracy, speed and memory requirements of simulations on a large scale.
Simultaneous Water and Gas Injection Pilot at the Kuparuk River Field, Reservoir Impact
Authors: Ma T. D. , Rugen J. A. , Stoisits R. F. , Youngren G. K.
Published: December 2007

Immiscible water-alternating-gas injection has effectively managed produced gas at the Kuparuk River Field, increasing field oil rate and recovery. Although I WAG economics are very favorable, a pilot study was undertaken to ascertain whether the separate gas injection system can be eliminated by simultaneously injecting water and gas in waterflood lines.

Static mixers were found to be necessary to disperse gas in a multiphase mixture flowing through a network of pipes. However, scale-up criteria for gas dispersing static mixers in multiphase pipe networks require additional refinement.

Reservoir simulation done to support the pilot project showed that simultaneous water-and-gas injection should provide better control of gas mobility than IWAG. This resulted in increased oil recovery and more steady gas production. During the typical IWAG process, the magnitude and the cyclic nature of GOR responses have caused problems for gas handling at the field facilities.

During the pilot, loss of injection rate was observed as the gas fraction in the injection mixture increased and the surface injection pressure was kept stable at about 2800 psi. Examination of Well 2D-16 data suggests that the observed rate loss was more likely due to the lower bottom-hole pressures than the relative permeability effects expected of two-phase flow in porous media.
Cavity Completion For Coalbed Methane Stimulation - An Integrated Investigation And Trial In The Bowen Basin, Queensland
Authors: Wold M. B. , Davidson S. C. , Wu B. , Choi S. K. , Koenig R. A.
Published: December 2007

Cavity completion stimulations have been trialled at two adjacent sites in the Bowen Basin, Queensland, Australia. The trials were conducted under thoroughly characterised reservoir conditions and were comprehensively monitored using multiple observation wells. Integrated with the trials were laboratory investigations of the fundamental mechanisms of cavitation in similar coals. These studies primarily comprised cavitation of coal blocks under full scale stress and pore pressure conditions, and numerical modeling of both the field and laboratory processes using both continuum and discontinuum models. Stimulation mechanisms are discussed in terms of two-phase flow, coupled mechanical - fluid flow in fractures, and coal failure under dynamic conditions.
Injectivity and Gravity Override in Surfactant-Alternating-Gas Foam Processes
Authors: Rossen W. R. , Kibodeaux K. R. , Shi J. -X. , Zeilinger S. C. , Lim M. T.
Published: December 2007

Surfactant-alternating-gas (SAG) foam processes can in principle combine high gas injectivity with low mobility at the front of the foam bank. Such a process can give the appearance of extremely shear-thinning behavior, in that the pressure gradient is remarkably low near the well. However, this appearance is due to the effects of declining water saturation near the well, not to the effects of high near-well flow rates on foam mobility. Preliminary simulation results suggest that as long as mobility is low in a region away from the well, high gas mobility near the well need not lead to gravity override. Indeed, since increased injectivity allows higher injection rates and thereby increased flow rates and pressure gradients away from the well, increased mobility near the well may help to reduce the risk of gravity override.
Experimental Evidence for Improved Condensate Mobility at Near-wellbore Flow Conditions
Authors: Boom W. , Wit K. , Schulte A. M. , Oedai S. , Zeelenberg J. P. W. , Maas J. G.
Published: December 2007

The inflow performance of gas wells in gas/condensate fields may be impaired when condensate banks form near the wellbore as a result of the pressure dropping below the dewpoint. This impairment may be alleviated to some extent, however, by the increase in condensate mobility at the prevailing conditions, which are characterised by high gas flow rates and relatively low interracial tension. Scouting reservoir simulations indeed identified this mobility improvement to be a key uncertainty in well-deliverability forecasting for gas/condensate reservoirs.

Model experiments with core material from various gas/condensate reservoirs in Europe and the Middle East were therefore conducted at ambient conditions to assess the degree to which the mobility of condensate could be improved by the applied flow conditions. A wide range of relative permeability and of saturation were probed, and several orders of magnitude of capillary number, interfacial tension and absolute permeability were covered. In all cases, the results reveal a truly significant mobility increase. Moreover, it was experimentally demonstrated that the key parameter controlling this effect is the capillary number and not the interfacial tension alone. The dynamic relative permeabilities that were obtained from our experiments are currently being used for history-matching well tests with equation-of-state reservoir simulations.
Reservoir Performance History Matching Using Rate/Cumulative Type-Curves
Authors: Callard J. G. , Schenewerk P. A.
Published: December 2007

This paper presents an analysis technique for characterizing reservoirs from production performance. Unique to this technique is the incorporation of the instantaneous bottom-hole flowing pressure (BHFP) to both the production rate and to the cumulative production for a well depleting a reservoir. This allows a single rate/cumulative analysis for wells producing with constant BHFP, constant rate, and wells with variable rate or variable BHFP (including wells with shutins). This solution provides a powerful diagnostic type-curve which can be generated with almost any wellbore/reservoir situation encountered. Extension of the method to gas reservoirs through use of pseudopressure and viscosity-compressibility normalization allows these wells to be analyzed using the slightly-compressible fluid solution. Well performance during transient flow and depletion flow are examined. Simulation results are compared with the analytic solution. The use of spreadsheets to perform well test analysis is also demonstrated.
Numerical Simulation of Waterflooding in a Pancake Oil Column
Authors: Evans David E.
Published: December 2007

The H-21 Reservoir in the North Alazan Field is a South Texas, Frio Sand reservoir. It has a thin oil column, overlain by a large gas cap and underlain by water. Applicability of conventional waterflood prediction techniques was questionable as the prediction techniques was questionable as the pancake nature of the oil column could result pancake nature of the oil column could result in losing oil to the gas cap when waterflooding. A waterflood study utilizing a two dimensional, three phase, numerical, reservoir simulator was undertaken to evaluate the waterflood potential. Results simulating reservoir behavior in a cross-sectional model with several water injection patterns and injection rates showed that none of the schemes would substantially increase oil recovery in the reservoir due to uncontrollable migration of oil into the gas cap.

Introduction

The North Alazan Field is located in the northeast part of Kleberg County, Texas, as shown by Figure 1. The H-21 Reservoir was discovered in December, 1958, by Humble's King Ranch Alazan No. 6 and by February, 1963, the reservoir was developed with 49 completions to 80 acre spacing. Studies of reservoir performance indicated a gas-cap-expansion primary drive mechanism, aided by a pressure-maintenance, gas injection program and hindered by severe gas coning. Ultimate recovery was projected to be 22 percent of original oil in place. A study was begun to evaluate the waterflood potential of the reservoir as a means of potential of the reservoir as a means of increasing ultimate recovery. The pancake nature of the reservoir (the H-21 Reservoir has a thin oil column, overlain by gas and underlain by water) required the use of a reservoir model employing numerical simulation to select the waterflood scheme with the most potential.

This paper discusses how the numerical simulator was used to model the reservoir under waterflood and discusses the results of six waterflood schemes which were evaluated.
Occurrence of Cemented Reservoir Roof Rock And Geopressure Caprock and its Implication in Petroleum Geology and Geohydrology
Authors: Fertl W.H. , Timko D.J.
Published: December 2007

Diagenesis comprises processes of transformation through which, as a function of pressure, temperature and depth, compact rocks are formed from unconsolidated sediments. Interspace in such consolidating sediments generally is filled with aqueous solutions, by far exceeding in quantity local accumulations of oil and gas. These interstitial solutions, their composition, movement, and mixing are important factors in diagenetic processes. The latter alter sandstones and clay minerals, both equally important in petroleum geology and geohydrology.

Of great significance is the occurrence of cemented layers which can readily be located and correlated by means of conventional well logs. Such cemented barriers occur as roof rocks, especially in structurally high positions in both oil or water bearing reservoir rocks, and as caprock sealing geopressured zones. Distribution of these cementing materials can be related to hydrodynamic conditions, planning of completions and the presence of abnormal pressure conditions. pressure conditions.

General Discussion

Compaction of argillaceous sediments causes movement of large amounts of aqueous solutions through the subsiding sedimentary column. While moving through sandstones and shales, the composition of these solutions may have changed many times considering the geologic time factor involved. Furthermore, any movement of formation waters across a sand/shale boundary will result in changes in the brine concentration in the sandstone. This is caused by the "salt filtering" effect of various clay minerals in respect to electrolytic solutions.

As early as 1933, it was suggested by Schlumberger et al that clays and shales act as semipermeable membranes and in 1947 the salt filtering properties of clays were shown experimentally by Buneev et al. A recent and excellent review of the relative factors influencing membrane filtration effects in geologic environments has been given by Berry 1969.
Pollution Control in the Oil Industry - From Spindletop to Santa Barbara
Authors: Langley William D. , Dunsavage Peter M.
Published: December 2007

Much of the modern character of the oil industry was established at Spindletop in the early days of the twentieth century. The industry has been a leader in technological developments since that time. But recent widely publicized incidents and the public's proper publicized incidents and the public's proper concern with cumulative contaminants in the environment have placed the industry in a defensive position. This paper presents an objective view of the industry's role in pollution control in a historical perspective and looks to its present and future efforts to preserve and improve the human environment coincident with technological progress.

Introduction

"A new engineering, a new chemistry, an awakened public opinion, and a more enlightened spirit in the industries of the country, are bringing on a new era in the control of industrial waste pollution." Editorial, Engineering News-Record, 1929 (1)

"…these activities of the various elements of industry point to the fact that industry in general is now in a much better position, but best of all is on the road to a position where the pollution controversy may cease to exist." W. B. Hart, 1946 (2)

"The same thing that characterizes mass initiative in general is true of industry; when anything goes wrong the remedy is long delayed." Amos L. Beatty, 1932 (3)

The news out of Beaumont the morning of January 10, 1901, was unprecedented in the United States. "Phenomenal" and "Incredible" were rather mild adjectives to apply to the "Solid Stream of Petroleum" rising out of the earth two hundred feet into the air at a rate later to be estimated as high as 100,000 barrels per day. For nine days the well flowed undiminished while frantic efforts were made to bring it under control. Beaumont became the scene of frenzied activity as people arrived from throughout the country to people arrived from throughout the country to profit from the dream of Patillo Higgins and the profit from the dream of Patillo Higgins and the persistence of Captain Anthony Lucas. While persistence of Captain Anthony Lucas. While few men had shared Higgins' obsession that oil would be found under Spindletop Hill, there were those who came forward with explanations after the event.
Automatic Casing Swabs: A Production System That Can Add Years of Productive Life to Wells
Authors: Cramer John W. , Wood Daniel D.
Published: December 2007

This paper will describe the operating theory, hardware, safe operating principles, and trouble shooting of Automatic Casing Swab(ACS) tools. Ananalysis of conversions will show that ACS are a viable production tool that can be used as an initial production method or be used to add years of productive life to wells.

A brief history and the operating principles of the ACS will familiarize the reader with the complex interactions of the various well components that can affect the successful operation of ACS tools. Examples of pressure transducers mounted in an operating ACS will offer some insight into the very dynamicnature of how an ACS tool operates.

The paper will share the knowledge and experience gained through 5 years ofchoosing wells to be converted to ACS. The paper will draw on one company's experience of installing and operating over 100 ACS in Ohio, New York, West Virginia, and Pennsylvania.

A criterion will be developed that assists the operator choose the wells that have the highest potential of benefiting from ACS technology. Some of the factors considered in developing this criterion are well history, decline curve analysis, gas to fluid ratios, and pressure analysis.

A discussion of the relative strengths and weakness’ of the various components of the ACS will be offered. This will allow the operator to recognize some of the critical factors, such as pipe roughness, that cannot bepractically measured but must be considered when selecting potential conversion candidates.

The paper will review the economic impact of the 100+ ACS well conversions. The costs associated with installation and conversion, changes in operating expenses, and differing production rates are considered in the overall economic analysis of the converted wells. The analysis will show that the ACS offers an alternative method of production that can be appropriate as an initial production method as well as a tool that can potentially add years of productive life to a well.
Dewatering of Coalbed Methane Wells with Hydraulic Gas Pump
Authors: Amani M. , Juvkam-Wold H. C.
Published: December 2007

The coalbed methane industry has become an important source of natural gas production. Proper dewatering of coalbed methane (CBM) wells is the key to efficient gas production from these reservoirs. This paper presents the Hydraulic Gas Pump as a new alternative dewatering system for CBM wells.

The Hydraulic Gas Pump (HGP) concept offers several operational advantages for CBM wells. Gas interference does not affect its operation. It resists solids damage by eliminating the lift mechanism and reducing the number of moving parts. The HGP has a flexible production rate and is suitable for all production phases of CBM wells. It can also be designed as a wireline retrievable system. We conclude that the Hydraulic Gas Pump is a suitable dewatering system for coalbed methane wells.
Performing In-situ Stress Tests With Water in Underpressured, Low Stress Zones
Authors: Fairchild Nelson R.
Published: December 2007

With the increased use of 3-D fracture simulators, the need for accurate and affordable formation stress tests has arose. One of the main factors in keeping the test cost down is conducting the stress test with water. In most formations the stress gradient is high enough (i.e. > 0.433 psi/ft) that water can be used, but there are many formations (Berea, Weir, Devonian Shale) that have stress gradients lower than 0.433 psi/ft. When this situation occurs the hydrostatic pressure of the water can fracture the formation and the well goes on vacuum. This leads to problems establishing constant injection rates and pressures that are usually obtained before monitoring pressure falloff1. In the past, formations with low stress gradients used nitrogen for the test fluid, thus keeping the hydrostatic pressure below frac gradient. This method works but is extremely cost prohibited.

This paper explains the problems that can occur when testing low stress gradient formations, and procedures that can be used to gain accurate formation stress profiles using water and a downhole shutoff tool with equalizing ports.
A Systematic Experimental Study of Acid Fracture Conductivity
Authors: Beg Mirza S. , Kunak A. Oguz , Gong Ming , Zhu Ding , Hill A. Daniel
Published: December 2007

The fracture conductivity created in the acid fracturing process is critical to the success of this stimulation method but is difcult to predict. We have conducted a series of experiments in which core samples were acidized in a cell that allows for linear flow through a vertical fracture with fluid loss through the cores. The fracture conductivity created was then measured as a function of closure stress. We find that increased acid contact time sometimes results in lower fracture conductivity, fluid loss can increase fracture conductivity, and the Nierode-Kruk correlation accurately predicts the effccts of rock embedment strength and closure stress on acid fracture conductivity. We also observed that high fracture conductivity is created when the acid forms a deep channcl in the fracture.
Chemical Removal of Formation Damage From Paraffin Deposition Part I – Solubility and Dissolution Rate
Authors: Fan Yong , Llave F. M.
Published: December 2007

This paper presents the results of experiments conducted to evaluate the solubility and dissolution rate of paraffin in selected chemical solvents. The causes of formation damage from paraffin deposition and the methods used to control or mitigate the damage are discussed. A thermodynamic model using regular solution theory was developed to predict phase equilibrium of solvents and paraffin precipitation. Reasonable agreement was obtained between the model prediction and laboratory results when the solvent compositions are known. The kinetic approach to the dissolution rate suggests the use of pseudo-first order reaction form between the paraffin and the solvent.
Formation Damage in Horizontal Wells Caused by Polymer Mud
Authors: Krilov Z. , Wojtanowicz A. K. , Tomic M.
Published: December 2007

This paper describes the results of formation damage study on first horizontal well drilled and completed in Croatia. The specific problem of formation damage caused by polymer mud was evaluated in the laboratory, investigating the rock-fluid compatibility and methods for restoring the reservoir permeability around the wellbore. The source of damage was identified as a vey tough mud filtrate cake as well as the reduction of permeability inside the pore space due to mud filtrate invasion. The two stages well stimulating procedure for damage removal, consisting of soaking and injecting oxidizer, then acid, in two steps, tested in the laboratory, showed promising results.
Quantifying Acid Placement: The Key to Understanding Damage Removal in Horizontal Wells
Authors: Jones A. T. , Davies D. R.
Published: December 2007

The placement of acid over the entire wellbore interval can be the key to successful stimulation treatments in wells with long (often horizontal) completion intervals. This paper discusses computer simulations performed to determine how fluids are distributed in the wellbore during bullheaded and circulated acidizing treatments. One of the novel aspects of these simulations is the inclusion of wellbore effects arising from the transient flow of acid and diverter along the wellbore. The results give an insight into a possible cause of some of the poor stimulation performances observed in the field when typical volumes of low-viscosity acids were injected without diversion or selective-placement techniques. Such situations can result in the acid coming into contact with only a small fraction of the treatment interval. The simulations also show how viscosifying the acid could have improved the stimulation performance.

This paper outlines the basic concepts of the simulations and some of the general trends observed from the results. In particular, the inclusion of transient wellbore flow calls for the modification of recently published guidelines for various diversion techniques.
Prefracturing Pump-in Testing for High-Permeability Formations
Authors: Chapman B. J. , Vitthal S. , Hill L. M.
Published: December 2007

Several types of prefracture injection tests, such as step-rate tests and minifracs, are commonly performed for optimizing frac-pack treatments. Originally, the industry developed most of these tests to diagnose the fracturi ng behavior of low-permeability, hard-rock formations. The analysis of these tests1 with bottomhole gauge data is reported in this paper. In addition, the execution and analysis of some of these tests have been modified in recognition of the differences between higher-permeability formations as compared to conventional low-permeability, harder-strength formations.

A matrix injection-falloff test (MlFOT) is proposed that can be used to estimate the approximate permeability and skin value of the formation before the frac-pack. This test can also help users determine fluid-loss behavior and identify possible reservoir limitations under certain circumstances. Step-rate/step-down tests are commonly used as a means of determining fracture extension pressure (FEP) and closure stress as well as identifying any near-wellbore restrictions or multiple fractures. Properly analyzed minifracs measure fluid-loss behavior of the fracturing fluid and also can be used to identify special problems, such as perforation friction, tortuosity, and multiple fractures. These parameters are then used to determine fluid volumes, pump rates, and proppant addition schedules for the actual treatment. Bottomhole gauge data from several wells indicate that near-wellbore tortuosity or perforation restrictions are not a major concern for Gulf of Mexico formations. However, there is some evidence of multiple fracture propagation.
Application of Risk Analysis to Screen Exploration and Development Prospects
Authors: Sharp W.R. , Kidd R.D.
Published: December 2007

Introduction

The exploration for, and development of oil and gas reserves is one of the major risk ventures undertaken by industry. This characteristic has been recognized, and industry has been willing to accept the risk involved in order to satisfy our nation's needs for energy resources. The existence of this risk is not unique to the oil and gas industry, but its nature is quite interesting and has, therefore, been the subject of much serious study.

To clarify what we mean by risk and risk analysis, let's look at the definitions. Risk is defined as a possibility of loss; analysis is possibility of loss; analysis is defined as an examination of a complex; therefore, used jointly they would refer to the examination of a complex possibility of loss. Those involved possibility of loss. Those involved in the search for accumulations of hydrocarbons recognize that this search does involve a very complex, and quite possibly loss of time, effort, and investment.

Having recognized the risk and defined risk analysis, the next question is how to apply risk analysis to exploration and development prospects. Prior to discussing this Prior to discussing this application, it is appropriate to examine the need for risk analysis.

The proper management of any company, regardless of size, involves the establishment of, and reaching for, several goals. These goals which include profit, survival, liquidity, and leadership, must be considered in making capital investment decisions. This is true of all companies but is perhaps amplified in the management of smaller firms where less capital is available for investment.
How to Stimulate Deep Hunton and Morrow Horizons in the Anadarko Basin
Authors: Ernst E.A. , Hurst R.E.
Published: December 2007

The deep horizons of the Anadarko Basin pose many problems in the drilling, completion pose many problems in the drilling, completion and production of wells. This paper deals with the problems and solutions for stimulation and production maintenance. production maintenance. The weaker, less efficient organic acids were commonly used to stimulate the Hunton zone because of corrosion problems at the bottom-hole temperatures. This problem has recently been overcome by using calculated cool down fluid volumes prior to injection of acid solutions into the well. New friction reducers have been developed to reduce friction pressures during treatment and this in turn allows higher injection rates and minimizes tubing exposure to acid solutions.

The fracturing treatments, in the Morrow zone, have also been limited because of elevated temperatures adversely affecting the treating fluids. The cool down approach has been used here also in order to realize greater fluid viscosities and to provide more efficient prop transport. A new fluid system has recently prop transport. A new fluid system has recently been used in the lower Morrow where rates were limited and adequate viscosity was essential.

The production of these wells has created problems because of corrosion and scale problems because of corrosion and scale build-up that severely restricts well capabilities. Many attempts have been made to adequately control corrosion. A recently completed well was squeezed with a corrosion and scale inhibitor. This paper also deals with the latest procedures that have been used to clean up procedures that have been used to clean up scale that has created wellbore restriction and loss of production.

The Hunton and Morrow intervals are productive throughout the Texas Panhandle and in productive throughout the Texas Panhandle and in Western Oklahoma, but the most recent and extensive activity has been in Hemphill County, Texas. The main areas of concern for this paper are the Buffalo Wallow and Washita Creek paper are the Buffalo Wallow and Washita Creek gas fields.
Deep Well Tubular Design Considerations
Authors: Odum Marvin E.
Published: December 2007

The tubular program of the ultra-deep well represents a major portion of the initial well costs, relates directly to probability of economically reaching projected depths and plays a continuous role in determining profitability during the well's productive life. productive life. This paper reviews, in general terms, tubular safety factor considerations, compatibility of tubular material and end finish with well environments, and hole and pipe size combinations.

Introduction

The ultra-deep well is defined as one which is 18,000 to 28,000 feet deep. Drilling and completion technology for each well varies according to projected depth and anticipated downhole environment, such as high pressures, sour gas, clearance problems, etc. A particular set of conditions dictates tubular design considerations, and similar conditions found in like wells of various fields and basins; therefore, there can be a deign relationship between ultradeep wells of two different fields (Buffalo Wallow and Washita) or two different basins (Delaware and Anadarko). For this reason, a general review of leading tubular designs for areas of ultra-deep drilling should be informative.