bluuebunny/crossref_metadata_2025 huggingface dataset:
Oil Supply and Demand Analysis: A Price Forecast for the Post-Iran-Iraq War Period
Authors: Zaid A. M. , Whitman D. L.
Published: December 2007

There is great uncertainty about the supply and demand and price of petroleum products. The semi-free market environment that existed prior to 1973 has long since disappeared. The political and economic situation of the world is becoming even more complex and unpredictable, resulting in greater uncertainties in commodity prices in general and petroleum products in particular. In the last two years we have seen wild fluctuations in oil prices that ranged anywhere between $30 per barrel to $9 per barrel. These sharp cycles in prices have made it virtually impossible to predict the next price cycle, which makes forecasting future exploration, drilling and production almost a futile excerise.

The prospect of a ceasefire between Iran and Iraq has pushed oil futures higher due to the belief that such a ceasefire would lead to greater cooperation within OPEC. The contention that the oil prices would increase as a result of the ceasefire is speculative in nature and does not take into consideration factors such as production history, reserves and a possible economic slowdown in the Western economies following the present expansion.

In this paper, production and reserve figures were examined for OPEC in general and Iran-Iraq in particular. Based on these figures, a production rate was forecasted for OPEC which was added to the non-OPEC production. The combined rate was matched with calculated future demand figures based on the forecasted growth rate in the Western and other economies.

Knowning the probable supply and demand, the the study covers the next five years which will possibly be the most turbulent, at least as far as the oil prices are concerned.

It was concluded that oil prices will remain in the 15-18 dollar/barrel range until 1995. After 1995, an upward pressure on prices could develop, but price increases will not be as dramatic as the increases seen in 1973 and 1980.
Protecting Foreign Risks
Authors: Mansbach B. T.
Published: December 2007

With the downturn in the U.S. oil economy, petroleum engineering and service companies are increasingly looking overseas for work. Many of the exciting developments in the petroleum industry are taking place in the developing countries, requiring parties to accept unique foreign risks. These risks can, in many cases, be covered by a small number of private sector political risk insurers and the Overseas Private Investment Corporation ("OPIC"), a U.S. Government agency, which offers political risk insurance and, to a limited extent, financing for American companies with exposures in the developing countries. This paper describes how those risks can be insured.

The Overseas Private Investment Corporation ("OPIC") is a United States Government agency designed to promote the economic development of less-developed nations by assisting United States citizens, corporations and their wholly-owned (95%) foreign subsidiaries in efforts to invest, or develop contractual relationships, in the third world. As a complement to the U.S. Agency for International Development, which finances projects on a government-to-government basis, OPIC's purpose is to facilitate the transfer of U.S. capital, technology and management skills by helping American companies establish a broad variety of projects in Latin America, Africa, the Middle East, the Indian Subcontinent, Asia and parts of Europe (Portugal, Greece, Yugoslavia, Ireland and Northern Ireland). Its political risk insurance and finance programs operate either independently of or in conjunction with the programs of the Export-Import Bank of the United States, the World Bank (including the International Finance Corporation), the regional development banks, foreign government supplier credit and political risk insurance agencies and private political risk insurers throughout the world. While Congress views OPIC as a development agency, corporate America views OPIC as an insurance company and a source of non-recourse (or project) financing.
A Large-Scale Planning and Evaluation Tool for Upstream Oil and Gas Operations
Authors: Blackburn C. R.
Published: December 2007

APEX is a large scale planning and evaluation model which simulates management decision making under a wide range of variation in the external environment. APEX selects projects for each year of a planning period based on recommended decision criteria and annual capital constraints. APEX is used for a wide variety of strategic planning studies, economic analysis problems, gas contract studies, acquisition and divestiture studies and the large scale, detail long range plan for the company with thousands of capital projects.
Closure Stress Profiling and 3D Fracture Simulations of the Staged Field Experiment Well No. 2, Upper Travis Peak Formation, East Texas
Authors: Miglicco T. P. , Moschovidis Z. A. , Veatch R. W.
Published: December 2007

The Staged Field Experiment (SFE) Well No. 2 is the second of four wells funded by the Gas Research Institute (GRI) for the advancement of research in fracturing and completion technology. This tight gas well is located in a lease owned by Amoco, in the North Appleby Field, Nacogdoches County of East Texas. The well is completed in the Travis Peak Formation which is a sequence of sand shale layers found from 8,000 to 10,000 ft. The permeability and porosity average approximately 0.05 to 0.08 md and 5 to 9 %, respectively.

Extensive pre- and post-fracturing tests were conducted by a consortium of academic and industry participants under the direction of a main GRI contractor. These include the stress testing of 25 zones and two mini-fracturing treatments ranging in volumes up to 6550 bbls. This paper derives a closure stress profile and possible variations using these data and related field experience, and simulates the main fracture treatment using a three dimensional fracture simulator. The simulations suggest fracture width reduction (pinching) at the perforations because of the presence of a low stress zone below and unsymmetric fracture height growth.1 Significant fracture height is indicated by both field data analysis and simulations. Fracture treatment design strategy is significantly affected by this occurrence, which suggests changes to common fracture design practices of many operators in the area. The simulations are compared with post-fracturing field data analysis to assess the resulting fracture geometry and the predictive capabilities of the simulations. Fracture design strategies are suggested for the area resulting from the experience gained from the SFE No. 2 well.
Volumetric Sweep Improvement in the Heterogeneous Tyler Sand of Central Montana
Authors: Mack J. C.
Published: December 2007

Waterflooding is a way of life in the Pennsylvanian Tyler formation in Central Montana; but not without problems. The heterogeneous nature of Tyler sandstone causes premature water breakthrough, water recycling, poor aerial and vertical sweep, and low oil recovery.

New technology to address these problems and improve waterflood performance has been implemented in six Tyler reservoirs in the past ten years. Polymers coupled with gelling agents are used to improve vertical conformance and flood efficiency. Much has been learned on how to better flood the Tyler.

This paper: Reviews the engineered oil recovery projects by defining the program, showing performance and evaluating the success of each project.Discusses the volumetric sweep improvement technology used and improvements made.Makes recommendations on "How to Flood the Tyler".
A View of Natural Gas Transportation
Authors: Ferries N. R.
Published: December 2007

The transportation of natural gas has been defined by some as the movement or conveyance of natural gas from the area of production to the market or ultimately the consumer. The subject paper describes the evolution of state and federal regulations imposed on the transportation of natural gas. The paper also discusses in detail the various FERC transportation programs which producers, pipelines, local distribution companies, and brokers can use to transport natural gas to markets throughout the United States. Finally, the paper discusses Chevron's participation in this evolving transportation environment as seen from the largest producer of natural gas.

In conclusion, with the natural gas industry changing its structure for transportation programs so quickly, it is imperative that an understanding of today's transportation programs and regulation be achieved. This paper outlines the structure of transportation regulation as well as develops an understanding for the FERC transportation program available today.
Impact of FERC Orders on Regulation of Gas in New Mexico
Authors: Lyon V. T.
Published: December 2007

FERC Orders 380, 436, 451, 490 and 500 promote competition among suppliers of gas for the benefit of the consumer and provide access to transportation of gas directly from producer to consumer. The "unbundling" of gas services has restructured the interstate pipelines and caused producers either to market their own product or find a broker. The disruption of contracts has upset the producer, pipeline and state regulatory agencies. Setting allowables, reporting gas sales, payment of taxes and royalty, and accounting to non-operating working interests are more difficult to administer and correlative rights are being confused.

The New Mexico Oil Conservation Division has changed some procedures to cope with this rapidly changing situation. More changes will be needed to do our job under the state's Oil and Gas Act. The priority system designed to keep hardship wells producing and casinghead gas flowing is in jeopardy. The State's role in preventing waste and protecting correlative (property) rights must be recognized by Federal agencies.
Improved Safety and Reduced Costs for Gas Piping Maintenance
Authors: Cohen J. H. , Pittard G. T. , Wilkey M. L.
Published: December 2007

REMS is a new system for reducing costs and improving safety of repairing buried utilities. This paper describes the design and operation of the REMS equipment and field test results. In addition to enhancing safety by nondamaging excavation, economic modeling (presented in the paper) shows the equipment can reduce current repair costs by as much as 50 percent through increased productivity and reduced restoration.
Recovery Optimization in a Bottom/Edge Water-Drive Gas Reservoir, Soehlingen Schneverdingen
Authors: Cohen M. F.
Published: December 2007

A reservoir simulation study of a water-drive gas reservoir, the Soehlingen Schneverdingen Sandstone, was carried out in order to estimate its gas in place and to determine production strategies which optimize the ultimate recovery.

The reservoir study was performed with Mobil’s black oil simulator, ALPURS, and followed closely the representation set forth by the log analysts and production geologists, which determined the geologic zonations and many of the reservoir parameters and trends. During the history-match phase, the critical match parameters proved to be the vertical communication and the aquifer size in comparison to the gas-cap size. The vertical communication could be specified from a coning study of a well producing water, and from diverging shut-in pressures which developed between two wells in the field. The aquifer si?e in comparison to the gas-cap size could be determined within limits from the differing pressure developments at the producing wells.

The prediction phase of the study revealed the somewhat surprising result of gas pockets being left behind even by structurally-high wells. This is a consequence of the water front cusping into the wells before the pressure level in the gas zone could be completely reduced. The thin layers of tight vertical permeability also contribute to this effect by reducing communication within the gas cap.

Several alternative production strategies were investigated in detail, such as accelerating the gas production to "outrun" the water encroachment, producing large amounts of water in one well after it waters out to slow the water movement to the other wells, and varying the location and the timing of additional wells. The accelerated production and other timing effects do not appear in this case to provide a significant improvement in the ultimate recovery. Water production, however, would be beneficial under certain circumstances, provided that the water could be economically disposed of. After accounting for the technical feasibilities as seen today, the various management proposals could be evaluated for the future development of the field.
Natural Gas Separation From Arsenic Compounds
Authors: Block-Bolten A. , Glowacki K.
Published: December 2007

Methods of removing arsenic compounds from natural gas and accompanying water to meet environmental requirements are discussed. Purification methods to remove arsine are evaluated and some are given preference. Data about process emissions from existing technologies are adopted. Most interesting patents including pyrolysis, adsorption, and absorption are listed. Potassium permanganate method is chosen as the most appropriate method to remove arsenic compounds from natural gas. Batch process to treat reservoir water and to regenerate the aresenic-saturated solutions and suspensions of potassium permanganate is recommended. The chemistry and thermodynamics of water conditioning process is presented.
Partial Oxidation Reactions of Methane and Oxygen
Authors: Droege M. W. , Hair L. M. , Pitz W. J. , Westbrook C. K.
Published: December 2007

In considering the typical experimental conditions used for studies of methane oxidation to oxygenates or hydrocarbons in the presence of catalysts, it is clear that a significant potential exists for the appearance of non-catalyzed, thermally activated gas-phase reactions of methane and oxygen. Experimentally, in a quartz reactor at 800 °C with a 3:1 methane-to-oxygen ratio and residence times of the order of 5-10 sec, significant conversion of methane (30%) to light hydrocarbons and COx with appreciable selectivity (25%) to C2+ components is observed due solely to these background reactions. In order to identify and describe the contribution of the gas phase processes during catalyzed reactions, a chemical kinetic model (HCT) developed at this Laboratory has been employed to describe these homogeneous gas phase reactions. Overall, the model predicts very well the trends and steady state results observed when tested against a series of experimental reactions comparing the effects of various reaction parameters such as residence time, temperature, and gas composition. The ability to accurately predict the magnitude of these background reactions should provide a means to begin to dissect the contributions of thermal gas phase chemistry from those of solely catalytic action.

New catalysts materials containing niobium and lanthanum have been synthesized. It is observe that niobium alone at high loading levels is an oxidation catalyst facilitating the production of carbon dioxide. This behavior is modified when lanthanum is incorporated into the catalyst material. In that case, improved selectivity to oxidative coupling products of methane is observed. These results appear to be a consequence of catalyst interaction with the existing background gas phase reactions.
Production and Stimulation Analysis of Multiple Hydraulic Fracturing of a 2,000-ft Horizontal Well
Authors: Yost A. B. , Overbey W. K.
Published: December 2007

The performance of multiple hydraulic fracturing treatments along a 2000-foot horizontal well bore was completed in a gas bearing, naturally-fractured shale gas reservoir in Wayne County, West Virginia. Pre-frac flow and pressure data, hydraulic fracturing treatments, and post-stimulation flow and pressure data form the basis from which a comprehensive analysis was performed. Average field production from 72 wells was used as baseline data for the analysis. Such data was used to show the significance of enhanced production from a horizontal well in a field that was partially depleted.

The post-frac stabilized flow rate was 95,000 cubic feet per day (mcf/d) from 2000 feet of horizontal borehole. Under current reservoir pressure conditions, the horizontal well produced at a rate 7 times greater than the field current average of 13 mcfd for stimulated vertical wells. This increase in gas production suggests that horizontal wells, in strategically placed locations within partially depleted fields, could significantly increase reserves.
Multiple Fracture Height Measurements: A Case History
Authors: Smith M. B. , Reeves T. L. , Miller W. K.
Published: December 2007

Since the inception of hydraulic fracturing, it has been recognized that fracture height is the dominant variable in designing or understanding hydraulic fracture growth. Later, this recognition was formalized with the development of fracture design theories by Perkins $ Kern, Gertsma deKlerk, and others. However, recognition of the importance of height is of little practical aid in the design or post analysis process for a fractured well. More recently, special production logs and open hole logs have been developed to address this problem and aid in fracture height prediction and measurement. These include, in particular, sonic log stress calculations and special spectral gamma ray logs and interpretation techniques. Also, the development of theories and models for analysis of fracturing pressures has been developed as a tool for estimating fracture height and fracture geometry. However, there is little field evidence where these various "tools" have been simultaneously utilized and compared.

This paper discusses a Rocky Mountain gas well case history where extensive testing was conducted to measure hydraulic fracturing characteristics. This included pre-frac lpg predictions of in situ stress and fracture height, in situ stress tests, pressure measurements and model calculations, and post frac temperature/gamma ray logs. The total fracture height (as well as differences in upward and downward growth) as predicted (or measured) with each technique is compared and critiqued as to its reliability and usefulness for this particular application. Of particular interest is the fracture width profile as measured with liquid RA tracer, and the changes in this with time as the fracture apparently closes. The significant differences in RA logs for liquid tracer and post-frac logs for tagged proppant are also significant. Finally, post-frac production and flow/build-up test results are compared to fracture design lengths.
Transient Pressure Analysis and Performance of Gas Wells Producing Under Constant Pressure Conditions
Authors: Berumen-C. S. , Samaniego V. F. , Cinco-Ley H.
Published: December 2007

This work shows the results of a systematic study of transient pressure analysis of gas flow under either constant bottom-hole pressure conditions or the constant wellhead ‘Pressure conditions. The effects of formation damage, wellbore storage and highvelocity ‘flow are included in the model. The analysis of simulated well tests showed that the interpretation methods used for liquid flow are generally accurate when the m(p) is used. For these conditions, a graph of 1/qD vs log tD presents gradually lower values than the exact conventional value of liquid flow of 1.1513 as the value of pwf decreases; for pressure buildup conditions a graph of mD(1,ΔtaD)/qD(ΔtaD=0) vs (taD+ΔtaD)/ΔtaD shows values of this siope witnin 1% of tfte 1.1513 vaTue. The maximum error was in the rate performance simulated cases that included high-velocity flow, being less than 13%. This upper limit occurs when the formation has a relatively "high" permeability (around lmd) and the rate performance test is affected by high-velocity flow. It was found that pressure buildup tests are superior to rate performance tests because high-velocity flow does not affect the slope of the straight line portion of the buildup curve.
Effects of Phase Segregation on Buildup Test Data from Gas Wells
Authors: Olarewaju J. S. , Lee W. J.
Published: December 2007

This paper considers the influence of wellbore phase segregation effects on pressure buildup test data. Wellbore phase segregation is a phenomenon that occurs in a well that is shut in with gas and liquid in the wellbore leading to an anomalous increase in wellbore pressure. This paper presents the use of pressure derivatives to identify phase segregation distortion and to differentiate this distortion from behavior of dual porosity reservoirs. Practical analysis techniques are presented for such tests. Using an automatic history matching technique, four field examples of buildup tests distorted by wellbore storage and phase segregation are analyzed.
The Effects of Operating Conditions, Reservoir Characteristics and Control Methods on Gas Kicks in Oil Based Drilling Muds
Authors: Rommetveit R. , Blyberg A. , Olsen T. Lie
Published: December 2007

A number of parameters influence the development of gas kicks in oil based drilling muds. The dynamic effects of operating conditions (drilling rate, pump flowrate, well depth and casing depth), reservoir characteristics (permeability and formation pressure) and control methods (drillers and wait and weight methods) have been studied with a dynamic simulator for gas kicks in oil based muds. The model accounts for the effect of pressure, temperature and gas solubility on the mud density, and the mass and momentum balance equations are solved to give the detailed pressure and flowrate distribution in the well as a function of time.

The control phase is studied in two kick cases; a distributed kick and a concentrated kick. A perfect control is performed using wait and weight and drillers methods, and the corresponding surface and casing shoe pressures are analyzed.

The study also identifies the most sensitive parameters for kick development, and gives guidelines on how to optimize the drilling operations related to well control.

The simulations are also analyzed with relation to early surface detection of kicks, and the most sensitive detection parameters are identified.
Restart Protection for Pipelines Transporting Paraffinic Crude Oil
Authors: Wheeler Gale , Gouhie Hugo , Laskowski Frank
Published: December 2007

The use of pour point depressants to provide pipeline restart protection in systems transporting paraffinic crude оil is dramatically illustrated by the successful restart of the Kotter system after an unplanned three week shutdown. This unfortunate event created an infrequent opportunity to compare predictive laboratory generated data with actual field restart data.
Field Experience in Down Hole Annulus Safety Valve
Authors: Geyelin J. L.
Published: December 2007

It is now a standard practice to equip production strings of offshore wells with SC-SSV's. Although there are no rules concerning the use of Down Hole Safety Valves in an annulus submitted to gas injection for gas lift purpose, concerns have been raised about the availability and implementation of such equipment.

This paper reviews the experience of T.CFP in Down Hole Annular Safety Valves that started 8 years ago. It covers the field experience of Annular Safety Valves in single and dual completion.
New Method for Determining Downhole Properties That Affect Gas Migration and Annular Sealing
Authors: Sutton D. L. , Ravi K. M.
Published: December 2007

Cement sealing of the casing-borehole annulus and gas migration control following primary cementing are closely related to real-time downhole fluid loss rates during the cement transition period.1

A series of cement fluid loss tests on washed mud filter cake clearly illustrate that downhole fluid loss rates are strongly dependent on fluid loss rates of drilling fluid. Unless altered by reactive washes, the initial fluid loss rate of the cement is equal to the rate established by the drilling fluid filter cake, but after 60 minutes cement filtration time control contributed by cement fluid loss additive is readily apparent.

Using technology similar to hydraulic fracturing fluid loss rate theory,2 a method of predicting the real time fluid loss rate for cement on drilling fluid filter cake has been developed. This method uses data derived from (1) standard high pressure-high temperature (HP-HT) tests on the cement slurry, (2) standard HP-HT tests on the drilling fluid, (3) laboratory drilling fluid filter cake thickness, and (4) estimated downhole drilling fluid cake thickness.

A method was derived combining static gel strength development rate, downhole fluid loss rate, and well geometry to give a dimensionless evaluation number. This evaluation number, defined as the slurry response number (SRN), is a relative prediction of cement slurry performance for controlling gas migration. Its practical use is illustrated with a case history. A field survey shows a firm correlation between this new evaluation number and successful gas migration control.

The results of HP-HT fluid loss tests on drilling fluid filter cake are given and compared to standard fluid loss tests and to simultaneously measured static gel strength. The influence of pressure on fluid loss rates and static gel strength rates is illustrated. Mechanisms by which fluid loss affects cement bonding and gas migration are discussed.

A method for determining slurry permeability during the transition period is given and results relating fluid loss to slurry permeability and specific static gel strength levels are shown.
A New Approach to the Interpretation of Wellbore Images
Authors: Wong S. A. , Startzman R. A. , Kuo T-B.
Published: December 2007

This paper presents a new approach for identifying features from wellbore images. We have developed a prototype system which finds geometric primitives related to geologic events in wellbore images. Rules are used to mimic the reasoning process used by image interpreters in identifying features related to geologic or natural events.

In this approach, the system takes digital data and converts it to symbolic forms. The symbolic forms proceed through a network of blackboards representing different levels of abstraction. Additional information from relevant sources such as previous geological interpretations, well logs, or well data can be used to constrain interpretations or limit searches.

Knowledge based systems with a large visualization component require both high and low level vision expertise. Using a multiple blackboard approach allows us to create knowledge bases which are specialized in particular aspects of the simulated visual process. A master control knowledge base controls the direction of inference. The multiple blackboard approach to the visual problem allows us to modularize the solution process. As more robust pattern matching algorithms are developed, they can be inserted into the system to improve system performance.

The system is implemented on a microcomputer and consists of four parts: interactive wellbore analysis modules, inference engines, specialized knowledge bases, and pattern matching algorithms. The paper explains the structure of the system and shows a field example.
Effects of Crossbedding on Well Performance
Authors: Lord M. E. , Collins R. E.
Published: December 2007

The effects of cross-bedding on transient pressure well tests have been investigated using a combination of numerical and analytical mathematical methods. It has been shown that for systems in which cross-bed laminae are thin, and closely spaced, relative to formation thickness, wells exhibit a negative skin factor and an effective permeability that are dependent on the dip angle of the cross-bed laminae.
Determining Optimum Estimation Methods for Interpolation and Extrapolation of Reservoir Properties: A Case Study
Authors: Brummert A. C. , Pool S. E. , Portman M. E. , Hancock J. S. , Ammer J. R.
Published: December 2007

The accuracy of four-point estimation methods (simple averaging, fifth-degree bicubic spline, inverse weighted distance squared, and kriging) were compared in five reservoir layers using data sets consisting of five different reservoir properties (horizontal permeability, vertical-horizontal permeability ratio, thickness, porosity, and top of structure). This study had four objectives: (1) to determine if kriging could be applied to petroleum-related data sets; (2) to determine the optimum estimation method by layer for each reservoir property and to use that optimum method to assign values to grid blocks for use in a reservoir simulation study; (3) to determine if a correlation could be established between the optimum estimation method and a reservoir property; and (4) to determine if criteria could be established for choosing the optimum estimation method through initial evaluation of data set size, distribution, and spatial correlation.

Kriging was found to be the optimum estimation method in 10 out of 12 cases for data sets having a normal or lognormal histogram distribution and a stable overall semivariogram. Simple averaging and inverse weighted distance squared were optimum in the other two cases. Fifth-degree bicubic spline proved to be the optimum estimation method for data sets that did not have a normal or lognormal histogram distribution. Simple averaging was found to be the optimum method for data sets that did not have stable overall semivariograms because of limited data set size. These results show that kriging can be applied to petroleum-related problems with a relatively small number of data points as compared to kriging's usual application in the ore industry with much larger data sets.
Borehole Directional Radar System for Subsurface Scanning
Authors: Chang H-T.
Published: December 2007

This paper summarizes the progress in the development of the Borehole Directional Radar (BDR). The theory for using radar for geological mapping is shown, and the design and characteristics of the antenna are discussed. The results of field tests in rock formations under both dry and wet conditions are presented. Finally, possible applications of the BDR system are outlined.
Computer Emulation of Human Mental Processes: Application of Neural Network Simulators to Problems in Well Log Interpretation
Authors: Baldwin J. L. , Otte D. N. , Wheatley C. L.
Published: December 2007

The skill of experienced log analysts is emulated by a new computer technology called Simulated Neural Networks (SNNs). Two SNNs are applied to problems in log interpretation. The first SNN is applied to a trivial and conceptually familiar interpretation problem: learning to compute total porosity (PHIT) and apparent grain density (RHOMA) from log data and lithology inputs. The second SNN learned to identify lithofacies patterns as a response to input log data. Interesting and human-like results were obtained when these SNNs interpreted log data in a well which has been full bore cored from top to bottom. Both SNNs performed as well as experienced humans and at least as well or better than conventional sequential computer program interpretations of the same two analysis problems.
Gravity-Stable Nitrogen Displacement of Oil
Authors: Naylor P. , Frørup M.
Published: December 2007

A series of experiments to investigate secondary and tertiary, gravity stable, immiscible, nitrogen displacement of oil in the presence of connate water is presented. Both high and low pressure experiments have been conducted using water wet sandstone cores and dead oils. Effluent production was recorded and the spatial distribution of oil along the core was determined using a radioactive tracer technique.

Experimental results are presented for secondary nitrogen injection at different flow rates, connate water saturations and core orientations. In-situ saturation measurements in a low pressure experiment have revealed a residual oil saturation to gas of 0.15 after 68 days of drainage.

The results of a tertiary nitrogen injection experiment at low pressure are presented. The residual oil saturation to water flooding was 0.47. During the tertiary gas flood, an oil bank was observed to develop and the oil saturation decreased to 0.08 after 86 days of gas flooding. This experiment demonstrates that tertiary gas injection can result in significant oil production, even at low pressures where the process is expected to be least efficient.

Oil relative permeability data have been derived from the in-situ saturation measurements and permeabilities down to 10-5 observed.
An Analysis of Water Shielding in Water-Wet Porous Media
Authors: Walsh M. P. , Negahban S. , Gupta S. P.
Published: December 2007

This paper presents simulation results for water shielding in strongly water-wet Berea rock. The analysis of experimental data indicates three oil phase fractions; flowing, trapped and dendritic (refers to isolated oil fraction which is in contact with flowing oil phase), which are different for different Berea core samples. Model calculations demonstrate that the noted differences are significant and that data measured from one sample cannot be used to predict displacement performance in other samples. Berea rock exhibits relatively small amounts of dentritic oil; therefore, formulating a dendritic oil fraction in model calculations is not as critical as correctly estimating the trapped fraction. The trapped oil saturation can be estimated from the oil primary drainage and imbibition relative permeability data.

Model validation using only an oil trapping function is supported by good agreement between model and experimental oil recoveries over a wide range of water/solvent injection ratios for tertiary CO2 displacements of a West Texas oil from water-wet Berea rock. Also presented are the results of a parametric study to identify key variables and their effect on water shielding phenomena.
Mobility Control Using CO2 Forms
Authors: Yang S. H. , Reed R. L.
Published: December 2007

Mobility reduction caused by CO2 foams that are "stable" or "unstable" in the bulk phase was studied in Berea sandstone and San Andres carbonate outcrop cores at l00°F and 2000 psi. Depending on hydrophilicity, some surfactants led to foams having a favorable dependence on permeability and oil saturation whereas another did not. Foam mobility was found "shear thinning" at high flow rates and "shear thickening" at low rates. Bubble coalescence was investigated in relation to snap-off, transport and trapping.
Interfacial Phenomena in Miscible Gas Processes
Authors: Rao D. N. , Girard M. , Sayegh S. G.
Published: December 2007

The interfacial phenomena of wettability, adhesion, mass transfer, and phase behavior due to miscible hydrocarbon gas injection have been studied by the use of the sessile drop contact angle technique, qualitative adhesion tests, and visual phase behavior observations under reservoir conditions. This experimental study has been conducted using crude oils from three Canadian reservoirs, pure mineral crystals of quartz, calcite and dolomite to represent the reservoir rock, and ethane for the hydrocarbon solvent.

While one of the three reservoir crude oils, namely that of Beaverhill Lake, showed significant changes in contact angles upon miscible gas addition, the others did not. The changes observed in the Beaverhill Lake system constituted a shift from water-wet to intermediately-wet behavior. However, phase behavior effects such as solids separation and settling within the crude oil drop due to solvent injection were common to all three reservoir systems studied. This indicated that the observed phase behavior changes were not reflected by the contact angle measurements.

Qualitative tests for adhesion at the crude oil/mineral crystal interface were also conducted under reservoir conditions. In contrast to the response of contact angles, the adhesion behavior was affected both by the aging time of the interface and by the injection of a miscible gas. These experiments demonstrated the insensitivity of the contact angles to the phenomenon of adhesion at the oil/crystal interface. The adhesion tests further demonstrated that an oil drop could adhere to the crystal surface even after the heavy ends (like asphaltenes) had precipitated within the oil drop away from the interface. This indicated that the heavy ends may not be solely responsible for the interfacial adhesion effects. Furthermore, it was observed that the solvent-mixed oil drop, when moved to a new spot on the crystal surface, could redevelop the adhesive bond with the solid surface.

This study brings forth the importance of including interfacial phenomena, which affect the reservoir flow characteristics, as an integral part of designing miscible gas floods.
An Improved Method for Gas Lift Allocation Optimization
Authors: Nishikiori N. , Redner R. A. , Doty D. R. , Schmidt Z.
Published: December 2007

A new method for finding the optimum gas injection rates for a group of continuous gas lift wells to maximize the total oil production rate is established. The new method uses a quasi-Newton non-linear optimization technique which is incorporated with the gradient projection method. The method is capable of accommodating restrictions to the gas injection rates. The only requirement for fast convergence is that a reasonable estimate of the gas injection rates must be supplied as an initial point to the optimization method. A method of estimating the gas injection rates is developed for that purpose.

A computer program is developed capable of implementing the new optimization method as well as generating the initial estimate of the gas injection rates. This program is then successfully tested on field data under both unlimited and limited gas supply. The new optimization technique demonstrates superior performance, faster convergence, and greater application than the standard "equal slope allocation" procedure.
Experimental Study of Hydraulic Fracture Geometry Initiated From Horizontal Wells
Authors: El Rabaa W.
Published: December 2007

Horizontal wells drilled in tight formations are likely to be stimulated by acidizing and/or propped fracturing to increase productivity. Normally, to control the placement of induced fractures in these wells, they are completed for later stimulation, i.e., cement cased and perforated. Unlike vertical well fracturing, fractures in horizontal wells can be induced along, or inclined to, or crossing the horizontal section. This orientation depends on deviation of the horizontal section from the minimum stress direction.

An experimental study of fracture geometry from horizontal wells at various well azimuth deviations was conducted. Experiments were performed by applying triaxial loading conditions to rock blocks 6 × 12 × 18 in. surrounding cased and perforated boreholes. The borehole directions varied from 0 to 90 degrees from the applied minimum stress. Also, length of perforated interval was the second variable parameter in this study. After each experiment, rock blocks were sawed to observe the shape of induced fracture. The study showed that fracture geometry near the horizontal well is controlled by well deviation and length of perforated interval. From a stimulation viewpoint, the combined effects of these two parameters, if not investigated beforehand, may cause critical problems during fracturing. Laboratory observations indicated the following stimulation related problems: Creation of multiple fractures from the same perforated interval.Created fractures are nonplanar, with rough walls.Communication of fluid between the perforated section and fracture can occur through small channels.Interference between fractures conducted from separate perforated interval.

Based on this study several recommendations are presented to help eliminate some of these stimulation related problems.
Drilling and Completion of a Horizontal Lower Spraberry Well Including Multiple Hydraulic Fracture Treatments
Authors: White C. W.
Published: December 2007

The John Snowden Well No. 7 is a multiply hydraulic fractured horizontal Lower Spraberry well.

The principle stress directions were determened and the well was drilled in the direction of the least principle stress. This was done so that multiple fractures would radiate out at right angles from the horizontal well bore.

Isolation for the multiple fracture treatments was achieved by a cemented liner, tubing conveyed perforating, and bridge plugs.

Frac sand production was eliminated through perforating technique and tailing in the frac treatments with curable resin coated sand in the cased hole portion of the horiaontal well. An open hole section of the well required sand screens to eliminate the frac sand production.

The frac load water was produced from the well and then the open hole and four perforated intervals were individually swab tested.
Real-Time Fracturing Fluid Rheology Measurements With the Helical Screw Rheometer
Authors: Lord D. L. , Shackelford D.
Published: December 2007

The increasing complexity of hydraulic fracturing fluids has intensified the need for improved on-site quality control methods. The helical screw rheometer (HSR), considered by many to be merely a laboratory curiosity, is shown to have unique features which make it an ideal on-line fluid sampling and testing device for use during hydraulic fracturing treatments. These features are exploited in an HSR unit which has been successfully adapted to function in the field environment. Since its operation is based on microprocessor technology, implementation of instrument control, data acquisition, and data analysis functions have all required special consideration. This paper describes how these various instrument functions were made operational. Data acquisition and analysis functions are further illustrated with viscometric data collected with a number of different fracturing fluid base gels.
Underbalanced Perforating Design
Authors: Crawford H. R.
Published: December 2007

A review of perforating regimes is presented followed by equations and tables which provide provide design guidelines for: the minimum underbalance pressure necessary to provide clean perforations, andthe maximum underbalance pressure which can be tolerated without causing sand production.an underbalance pressure which is recommended.

The properties of the reservoir and of the adjacent formations are the independent variables of the equations. The work of previous investigators provides the foundation for these equations.

Several case histories are presented. They generally confirm the validity of the equations. They show the remarkable production increases that are obtainable with underbalanced, high density, perforating.

Data are presented which show the damage caused by killing a well which originally had clean perforations. Some of this damage was temporary. Laminated formations and perforating overbalanced are discussed.

A recommended method for selecting the perforating method and conditions is highlighted.
Comparison of HEC and XC Polymer Gravel Pack Fluids
Authors: Underdown D. R. , Calvert A. L. , Newhouse D. P.
Published: December 2007

Several service companies are promoting the use of XC polymers to replace HEC polymers in gravel pack fluids. The XC polymer system 1s advertised as providing better gravel carrying capacity and less formation damage than HEC polymer systems.

Results of laboratory and field tests with XC and HEC polymers show that the final properties of the fluid system are dependent upon mixing procedures. Hydration and shearing of the XC polymer system prior to the addition of the salt gives a gravel pack fluid with the most consistent fluid properties. High shear and filtration through too fine a filter causes severe loss of gravel carrying capacity and viscosity for both the HEC and XC systems. Filtration through a ten (10) micron absolute cartridge filter is the last step in the preparation.

Formation damage studies show that initial exposure to a XC polymer system causes minimal damage. The formation damage is minimized by proper mixing, proper filtration of the system and the proper amount of breaker. However, testing has shown that repeated exposure of the formation to the XC or HEC polymer systems after breaking causes substantial formation damage even with the proper mixing, filtering and breaker systems.
Successful Proppant Fracturing of Ultradeep Sour Gas Reservoir
Authors: Ely J. W. , Cobb W. J. , Elkin B. , Bell D. D.
Published: December 2007

During the past 3 years, a successful stimulation program has been completed with the fracturing of four wells in the Smackover formation. The four wells were stimulated in the Johns Field in Rankin County, Mississippi. The Smackover formation is located at 19,000+ feet and has a bottomhole temperature of about 330° F. The natural gas in the Johns Field contains about 31% H2S and 4% CO2.

Three of the four wells in the field had been fracture treated upon initial completion with moderate volume treatments and low concentrations of proppant. It was determined that procedures used in cleaning up these wells combined with the excessively large overburden pressure had reduced the effective fracture conductivity to essentially zero. The high bottomhole temperature (330° F) and high fracturing pressures (19,000 psi) essentially represents the current limits of both fluid technology and pumping equipment. A major effort was made to assure quality control of the fracturing fluid above and beyond that normally done on typical fracturing treatments. On site evaluation of all fracturing fluid using Fann 50 viscometers combined with normal quality control procedures was very beneficial in assuring that quality fluids were mixed and pumped.

Intensive reservoir and economic studies were made to evaluate the economic viability of the stimulation treatment prior to each treatment. All of the fracturing treatments have been financial successes and the productivity of the Johns Field has been increased by more than 300%. In fact, further drilling is underway based upon the results of these fracture treatments.
Reanalysis of the MWX Fracture Stimulation Data From the Paludal Zone of the Mesaverde Formation
Authors: Miller W. K. , Smith M. B.
Published: December 2007

To investigate Western U.S. tight gas sands, and in particular lenticular sandstone formations, DOE established the Multi-Well Experiment (MWX) near Rifle, Colorado. The field research facility consisted of three closely spaced wells drilled through the lenticular Mesaverde formation for the purpose of establishing production potential from lenticular reservoirs, and improving existing production technology for this unconventional gas source.

This paper presents a review and re-analysis of the fracture stimulation data from the Paludal zone. Two of the main objectives of the Paludal experiments were 1) to determine fracture geometry and "predict" behavior in a lenticular environment and 2) to successfully stimulate lenticular sandstones in a complex, coal-bearing interval. While the original Paludal testing and analysis was mainly successful in addressing these, there remained some questionable aspects; one being the unexpected, abnormally high treating pressures during the fracture tests and propped fracture treatment. These first Paludal zone tests were, in fact, one of the early observations of "abnormal" high fracture treating pressures.

To establish the seemingly abnormal fracture behavior, much of the raw stress data was reviewed and good correlations found to exist between in situ stress and lithology (gamma-ray) and acoustic velocity (sonic log). From the lithology correlation, a detailed stress profile was derived and used in a pseudo 3-D fracture simulator to history match the two minifracs and main treatment. While much of the re-analysis was in good agreement with previous work, some significant differences were found with respect to the stress profile, fluid leak-off, and prediction of bottomhole treating pressure (BHTP). In fact, from the re-analysis, the prediction of BHTP was relatively straight forward and the calculated fracture height from the simulator closely approximated that observed with post-frac logs and borehole seismic data. The results suggest another possible (and fairly simple) mechanism for the unexpected high treating pressures observed and noted in several recent publications - that is, vertical and lateral variations in fracture closure stress.