bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Rock Types With Mixed Wettability Using Log and Core Data – DOE Project Welch Field, Dawson County, Texas
Authors: Hinterlong G. D. , Taylor A. R.
Published: December 2007

In conjunction with the DOE Project (DE-FC22-93BC14990), the characterization of a portion of the Permian age San Andres formation under Welch Field, Dawson County, Texas was initiated. The objective of the characterization is the construction of a geologic model for the numerical simulation of a C02 flood of the reservoir. A detailed reservoir description is required because the high costs to inject and recycle C02 dictates a very efficient flood design. Identification of reservoir barriers, flow units, and prediction of continuity present the greatest challenge to the description. The productive portion of the formation is mineralogically simple, consisting of dolomite and anhydrite with very minor amounts of chert and illitic clay. Deposition occurred in a very flat shallow shelf setting ranging from supra tidal to subtidal. Depositional textures are variable ranging from fenestral mudstones to oolitic grainstones, with wackestones and packstones dominating. Diagenesis of these shallow shelf deposits has created a highly complex pore system which at times crosses depositional facies boundaries. Rock fluid interaction further complicated the descriptive process by affecting the log responses.

Porosity-permeability cross plots exhibited good correlation for a carbonate reservoir but were too coarse for simulation purposes. Special core analysis tests of capillary pressure and relative permeability provided the key for identifying the intervals of differing wettability and pore structure. A methodology has been developed to identify the varying pore systems and differing wettabilities, using multiple logs from a routine logging suite and special core analysis. The input from multiple log measurements provides a better estimation of the formation absolute permeability than by using a single porosity-permeability relation. These reservoir parameters could then be extrapolated to uncored wells, using the sequence stratigraphy framework, to build the 3-D model of the reservoir.
Pressure Transient Data Acquisition and Analysis Using Real Time Electromagnetic Telemetry
Authors: Doublet L. E. , Nevans J. W. , Fisher M. K. , Heine R. L. , Blasingame T. A.
Published: December 2007

This paper presents the operational procedures and the results for two pressure buildup tests performed using a wireless telemetry acquisition system (TAS) tool at the North Robertson (Clearfork) Unit (NRU) in Gaines, Co. Tx. Using a single pressure gauge system downhole, we obtained real-time telemetry of pressure and temperature data at the surface, as well as a larger sampling of data that were stored in the downhole memory system.

This new wireless telemetry acquisition system was developed to provide real-time pressure and temperature data at the surface by using an electromagnetic signal to transmit these data through the formation strata. The tool is fully programmable so that a wide range of sampling frequencies can be used. The system allows pressure and temperature data to be stored downhole (as in the case of a typical "memory" gauge), or these data can be transmitted to surface data acquisition systems. This provides real-time pressure and temperature data for pressure transient tests, stimulation monitoring, and long-term reservoir surveillance.

Our objective is to demonstrate the use of this technology for pressure buildup tests in low permeability reservoirs. Our goal in utilizing this technology is to reduce the shut-in time requirements for pressure transient tcsts-which will ultimately result in a more cost-effective reservoir surveillance program as wells can be returned to production (or injection) as quickly as possible.

Once the pressure data were acquired, we performed conventional semilog and log-log analysis, and we simulated test profiles to verify the analyses of the test data. Both surface and downhole pressure data were compared for consistency, and both types of data were analyzed in exactly the same fashion. The results of these analyses were essentially identical. This approach gave consistent estimates of reservoir pressure, permeability, skin factor, and fracture half-length for both of our case histories.
How Can Selective Mobility Reduction of CO2-Foam Assist in Reservoir Floods?
Authors: Tsau Jyun-Syung , Heller John P.
Published: December 2007

C02-foam has been long realized as an effective mobility reducing agent for C02 flooding in oil recovery process. Recent researches indicate that some C02-foams also show an exciting additional characteristic, selective mobility reduction (SMR), in which the mobility of foam is reduced by a greater fraction in high than in low permeability cores in laboratory experiments. Examples of such an unusual property are presented first in this paper to show the mobility dependence of C02-foams on the rock permeabilities ranging from 30 to 900 md. Secondly, a simple modeling procedure is introduced to evaluate the benefits of using an SMR displacing agent in a typical oil recovery process. In this model, the mobility of the displacing fluid is considered to be proportional to the permeabilities raised to a specific exponent. This allows us, for different values of exponent from zero to one, to examine how different degrees of SMR will affect the oil recovery. The modeling results show that, as expected, the breakthrough time of the faster (higher permeability) layer is delayed and the vertical sweep efficiency of the model is improved if the mobility of the injected fluid is reduced. Furthermore, this improvement becomes even more significant when an SMR fluid is used for the displacement. Even a slightly favorable SMR fluid, that shows a slight dependence of mobility on rock permeability, can significantly reduce the number of pore volumes required to achieve the same degree of recovery as that realized with an ordinary mobility reducing agent.
Effect of Capillary Contact on CO2-Foam Mobility in Heterogeneous Core Samples
Authors: Yaghoobi Hossein , Heller John P.
Published: December 2007

Early breakthrough and poor sweep efficiency are common problems in CO2 floods. These problems result from the large viscosity contrast between the displaced and injected fluids as well as from the heterogeneity of reservoir rock. Evidence shows the presence of an aqueous surfactant solution will produce a foam with CO2, which not only controls the gas mobility but may also selectively reduce the gas mobility through regions of differing permeabilities. Experiments were conducted to test the CO2 -foam behavior in composite parallel core samples where the two permeability regions are in capillary contact. These composite cores are more characteristic of reservoir conditions. This paper examined the effect of heterogeneity on CO2 -foam in composite cores contained coaxial zones of high and low permeability.

The results from these experiments indicate that the CO2 breakthrough was delayed in the high permeability region during the transient period when surfactant solutions were used. Without surfactant the flowing quality (fraction of CO2 in total injected fluid) was lower in the low permeability region as compared with that in the high permeability region. These results indicated the favorable fluid mobility in heterogeneous core samples when foaming agents were used.
Acid Sludge Characterization and Remediation Improve Well Productivity and Save Costs in the Permian Basin
Authors: Wong T. C. , Hwang R. J. , Beaty D. W. , Dolan J. D. , McCarty R. A. , Franzen A. L.
Published: December 2007

Many oil wells in the Permian Basin have reported sludging problems associated with acid stimulations. The acid sludge is similar among wells and was identified as a viscous emulsion stabilized by asphaltene-rich organic solids. The sludging tendency of the oil increased with the concentrations of asphaltenes and resins, base number of the oil, and ferric ion content in the acid. Only three out of nine commercial acid systems tested were effective in preventing acid sludge formation; they all utilize the same novel iron control technology, i.e., catalytic reduction of ferric ions. Several commercial and generic solvent systems were effective in dissolving acid sludge, including mixtures of an aromatic solvent (e.g. xylene) with either isopropyl alcohol (2:1 volume ratio) or EGMBE (2:1 to 3:1 volume ratios). Selection of acid formulations and solvent systems was based on cost effectiveness and operation safety. Field implementation proved successful. If the results of this study had been implemented earlier in the lives of some of the Permian Basin properties, the recovery of 574 BOPD of lost or deferred production from 99 wells could have been realized. This would have resulted in an estimated increased revenue of over $3 million in one year.
Hydraulic Fracture Technology in the Ozona Canyon and Penn Sands
Authors: Cipolla Craig L.
Published: December 2007

This paper details the acquisition and application of laboratory rock mechanical data, in situ stress measurements, dipole sonic logs, and pre- & post-fracture well test data to characterize hydraulic fracture performance in the Ozona Canyon and Penn sands, Ozona Field, Crockett County, Texas. The in situ stress measurements (micro-fracs) showed sand stresses from 0.55 to 0. 75 psi/ft, while shale stresses ranged from 0.8 to 0.85 psi/ft. These data were used to calibrate dipole sonic logs that ultimately resulted in lithology based (gamma-ray) stress profiles for fracture modeling studies. The variations in measured sand stresses using micro-frac tests indicated the need for small-volume water mini-fracs prior to many fracture treatments to measure local sand stresses.

Excessive treating pressures (high net pressures) indicated the possibility of complex fracturing (or multiple fractures) and this interpretation was supported by the short "effective" fracture half-lengths (+/- 200 ft) calculated from subsequent fracture modeling and pre- & post-fracture well tests. The post-fracture well tests unexpectedly showed very low fracture conductivity that was also attributed to complex fracturing. The inability to significantly improve "effective" fracture length with increasing fluid & proppant volumes resulted in reduced treatment sizes (and treatment costs) and improved well economics.
Field Results Demonstrate Enhanced Matrix Acidizing Through Real-Time Monitoring
Authors: Zhu Ding , Hill A. Daniel
Published: December 2007

The use of an inverse injectivity versus superposition time plot to diagnose the changing skin factor in a matrix acidizing treatment has been presented previously by Hill and Zhu1. The model has been extended to calculate skin factor as a function of injection time or injected volume directly to help the operator monitor and optimize the treatment. A Windows program based on the theory has been developed to provide a pretreatment test to evaluate the permeability and the initial skin factor of the formation when they are not available before the acid treatment, to calculate and plot the evolving skin during the treatment in real-time, and to evaluate treatments afterwards. It converts surface pressure, when measured, to the bottomhole pressure for the calculation, and handles fluid density and viscosity changes in real time. Several field examples showed that the technique can be used conveniently to monitor skin changes and diversion effects during matrix acidizing treatments. The program is reliable and flexible in acquiring and processing data, calculating skin, and diagnosing matrix acidizing treatments.
Simulation Studies of Waterflood Performance With Horizontal Wells
Authors: Ferreira H. , Mamora D. D. , Startzman R. A.
Published: December 2007

Two- and three-dimensional simulation studies have been done to evaluate waterflood oil recovery in a 40-acre 5-spot pattern using horizontal and vertical well systems. The three-dimensional simulation results indicate that the parameters considered, i.e. vertical permeability-horizontal permeability ratio, injection and production rates, and reservoir thickness have little effect on waterflood oil recovery for a particular water-oil mobility ratio. For both vertical and horizontal well systems, oil recovery decreases with increasing mobility ratio. It is concluded that the mobility ratio is the dominant parameter affecting waterflood oil recovery, in line with the experimental results of Craig, Geffen, and Morse1 for conventional waterfloods. Waterflood oil recovery using a horizontal well system is shown to be higher than that obtained by using a vertical well system. A correlation has been developed which expresses volumetric sweep efficiency in a hypothetical 5-spot pattern as a function of mobility ratio. This correlation would be useful for estimating waterflood oil recovery for the ranges of reservoir parameters considered.
Euler Loads and Measured Sucker Rod / Sinkerbar Buckling
Authors: Long Scott W. , Bennett Donald W.
Published: December 2007

The Petroleum Industry is experiencing anincreased awareness and understandingof sucker rod compression. This awareness has evolved during the past twelve years, from initial recognition of rod buckling, to a current desire to quantify (measure) the amount of compression required to initiate rod buckling.

Recent attention has focused on true or effective compressive loads in sucker rod strings. Measurement of these loads is being documented (1) and data collection is ongoing with improved technology.

This paper will provide a more accurate understanding of the amount of compression required to buckle sucker rods and sinkerbars of various diameters. This will be accomplished by presenting the following; Predictive compressive loads that buckle various diameters and lengths of sucker rods and sinkerbars utilizing Euler loads.Measured compressive loads that are required to buckle various diameter sucker rods and sinkerbars.A comparison of predictive compressive loads to measured compressive loads.

Knowledge regarding the amount of rod string compression required to buckle various diameter sucker rods will provide the industry better rod string design guidelines.

Use of these guidelines will help identify dangerous compressive rod string loads which initiate rod-tubing contact, provide associated wear, and result in rodand/or tubing failure.
An Integrated Study of the Grayburg/San Andres Reservoir, Cowden Fields, Ector County, Texas
Authors: Reeves J. J. , Smith W. H. , Trentham R. C. , Weinbrandt R.
Published: December 2007

A cooperative study of the Grayburg/San Andres reservoir is being conducted in response to the United States Department of Energy's (DOE) Class II Oil Program. The project is cost shared by Laguna Petroleum Corporation (operator), Latex Resources, Inc. (operator) and the DOE. The purpose of this study is to preserve access to existing wellbores by identifying additional reserves. Production problems associated with shallow shelf carbonate reservoirs are being evaluated by a technical team integrating subsurface geological and engineering data with 3-D seismic data. Engineering analysis, subsurface control from wireline logs, and 3-D seismic data will be integrated using a network of state-of-the-art software on a high performance computer workstation. The results of the integrated effort will be a recommendation for infill drilling locations and the design of an effective waterflood. It is expected that this study will demonstrate a methodology for reservoir characterization and subsequent development of the Grayburg and San Andres reservoirs that is feasible for even small independent operators. The integrated multi-disciplinary approach of reservoir evaluation is relevant to many shallow shelf carbonate reservoirs throughout the United States. Furthermore, this study will provide one of the first public demonstrations of the enhancement of reservoir characterization using high resolution 3-D seismic data. This paper discusses the geological makeup of the Grayburg and San Andres reservoirs and the acquisition, processing, and interpretation of the 3-D seismic data set acquired for the project. The 3-D seismic volume will be utilized for optimization of a reservoir simulation model through a quantitative study to extract reservoir properties from seismic attributes.
Predicting the Fluid Loss of Drilling, Workover, and Fracturing Fluids into a Formation With and Without Filter Cake
Authors: Carlson E. S. , Venkataraman M. , Clark P. E. , Sifferman T. R. , Coffey M. D. , Seheult J. M.
Published: December 2007

We present in this paper the theory associated with the invasion of power-law fluids in both radial and linear systems during drilling and completion operations. We have developed a computer model based on this theory, and present computational results which validate the model against analytical and experimental results. Calculations based on experimental parameters show that power-law fluids can be very effective in the control of invasion from the wellbore to the formation. Furthermore, the results show that this control does not come at the expense of long-term well damage, because it is easy to flow back the invaded fluid.
Acid Fracturing in the Warrent Unit of Southeastern New Mexico
Authors: Metcalf Steven , Ward Brian , Davis Wayne , Gray Daniel H. , Brienen Jeff , Miller Joe
Published: December 2007

The development of viscous acid systems has improved the effectiveness of acid fracturing. A specific case in point is the Warren Unit of Southeastern New Mexico, which produces oil and gas from the Drinkard, Tubh and Blinebry formations. The Drinkard and Tubb formations have been found to respond favorably to acid fracture stimulation through the use of gelled and crosslinked acid systems. A crosslinked 15% hydrochloric acid gel fracturing treatment provides an economic and effective initial stimulation of the Drinkard and Tubb, while re-stimulation of Tubb wells has yielded similar results independent of the treatment type.

Production results are evaluated for the different treatments. Included are comparisons of various viscous treating fluids and treatment procedures. Rotating disk reaction rate information, rheological properties of various fluids, fluid loss characteristics, formation lithological differences and well locations are also discussed. The limitations of usage of the various fluids and techniques within the Warren Unit are addressed.
Radioactive Tracers: Review of Principle Factors in Design and Application
Authors: McLaughlin James S.
Published: December 2007

Radioactive tracers have been successfully utilized to interpret the placement of stimulation treatments. Completion effectiveness can be verified best when stimulation operations are traced. The advances in tracer technology require a thorough understanding of all the factors that affect the design and use of tracers, including the commercial manufacture of nuclides, the economic benefits of their use, the regulatory and licensing requirements, the choice of materials and systems, exposure doses and exposure risk, procedures for well reversal (flow-back) and the technology behind multi-isotope logging (gamma spectrum analysis).
Low Cost Solutions for Well Interventions Through Advanced Slickline Services
Authors: Larimore David R. , Goiffon John J. , Bayh Russell I.
Published: December 2007

In the past, slickline service has been considered as an option suited only to routine mechanical well workovers. This is no longer the case. New technology has expanded slickline capabilities to include services for well interventions that have traditionally been reserved for other, more-costly alternatives. This paper will discuss the innovative equipment that has been developed to support this technological expansion, all of which plays an integral part in the expanded slickline concept, specifically: An electronic triggering device that provides a safe, efficient method for firing detonatorsA battery-operated, electro-mechanical tool that is capable of setting wellbore devices with slickline and braided line without explosives.An electronic measurement system that can automatically correct measurement inaccuracies resulting from line stretch and environmental stress factors.A collar locator that can provide verification of collar locations in a tubing or casing string.Data/job loggers or acquisition software systems that can be connected to the electronic measurement system to graphically record dynamic information that occurs during a wireline trip.A wireline inspection system that can determine integrity of both new and used mechanical wirelines during and before service.

Case histories will be used to provide comparisons of cost, operational efficiency, and enhanced safety features of traditional service options and the new advanced slickline system. Methods for service strategies that support current economic trends and well solutions will also be discussed as well as methods to determine key needs for appropriate service alternatives.

The combined use of these slickline tools provides a state-of-the-art service system that can provide efficient alternatives for the advanced service needs in the oilfield today.
Teamwork Installs Waterflood Expansion Project in West Texas on Tiime and Within Estimated Costs
Authors: Hollar E. A.
Published: December 2007

abstract

The installation of an $18.4 million waterflood expansion project in Phillips' Goldsmith Andector Unit (Gandu) was completed in ten months and within ten percent of original cost estimates. A multi-disciplined team effort was used throughout the project, from the earliest design and planning stages throughfinal equipment installation. The project included the drilling and completion of24 infill producing wells; conversion of 28 existing producers to water injection; construction of a fully automated, 35,000 barrels of water per day injection station and 11.5 miles of injection line.

The project design stage lasted more than a year and involved regular meetings ofthe Gandu Waterflood Expansion Premise Team. Team members represented a variety of disciplines and areas of responsibility. The project was then passed to an implementation team with similar diversity. The participation and input of all groupswas solicited and utilized throughout the development and implementation of the project.

The construction of a $1.2 million water station was completed in four months and within the original cost estimate. The identification and procurement of critical path items was essential for the timely installation of this facility.Another factor contributing to quick construction time was the development of detailed construction drawings. The team identified significant difficulties encountered in past projects that were due to poor communication between facilities and electrical construction groups. The installation of five miles of electrical conduit necessary to automate the water station had to be effectively integrated into the construction process, rather than worked in as an afterthought. The electrical group was provided with piping schematics early in the design process, which enabled the planning of ditching and conduit routing before construction ever began. The finalized drawings made possible the coordination of two construction groups and the quick installation of a complex facility.
Use of Rod Pump Database for Improving Artificial Lift Operations
Authors: Soza Roberto L.
Published: December 2007

abstract

The need for data management and analysis has become crucial to the continuous improvement programs initiated in many operations. In particular, focus on improving profitability dictates that efforts onimproving production and reducing operating costs be continuously applied. To accomplish improvements an effort was undertaken to improve the quality of rod pumps used in 1500 rod pumped wells in the Andrews area. As part of this effort, it was recognized early that in order to measure and instigate improvements, an effective means of capturing and analyzing data from rod pumps pulled from wells needed to be developed. A database was developed to store rod pump run and pull data captured on a standardized pump shop repair report form. Results from this effort (along with associated improvements that will not be covered in this report) have yielded pump failure frequencies that are 40% lower and pump repair job expenditures that are 60% lower.
Airphoto Fracture Analysis of the Cottonwood Creek Field, Bighorn Basin, Wyoming
Authors: Prost G. L.
Published: December 2007

Surface mapping can be used to evaluate reservoirs where fractures influence the flow of fluids. Fracture zones mapped at the surface appear to reflect structures at depth that act as impermeable barriers to flow across the zone and as conduits for fluid flow along the zone.

Airphotos were used to evaluate a fractured carbonate reservoir at Cottonwood Creek field, Bighorn basin, Wyoming. Cottonwood Creek produces from a Stratigraphie trap in the Permian Phosphoria Formation at depths from 1538-3077 meters. Surface lineaments were interpreted on color-infrared stereo airphotos (1:58,000) and then digitized. Contour maps were generated of total surface fracture density and fracture density within various trends. These maps were compared to subsurface data to determine if they had any relationship to reservoir properties.

The principal (northwest) fracture set is unrelated to production. A map of northeast fracture density shows intense fracturing that corresponds to zones of increased total porosity-feet and high cumulative production. Enhanced recovery programs must account for these fracture zones.
Using the TQM Umbrella to Implement Business Process Reengineering
Authors: Flatt Robert N.
Published: December 2007

This paper analyzes the keys to successful implementation of a Total Quality Management (TQM) effort in a major oil service company over a 13-year period. A formal Quality Improvement Process began in 1982 with an initial focus upon error cause removal, employee involvement, and cross-functional corrective action teams. During the 1980's the program targeted manufacturing processes: statistical process control, just-in-time manufacturing, process capability studies, vendor partnering, and industry QA standards such as ISO 9000. Cost of quality plummeted from over 30% of sales to less than 5% during this period. In 1993 all change efforts were brought under the TQM umbrella and the focus shifted to reengineering the key business processes of the company. This paper will describe in detail how the TQM program evolved from a softer, quality awareness, people involvement process to a very results driven, radical change effort focused upon reengineering the activities, processes and structures of our businesses to reduce cycle times of all business processes, reduce costs, and improve quality and customer satisfaction. We will discuss the change imperative facing our industry and the basic concepts and principles of Business Process Reengineering and Supply Chain Cost Management. This will include a discussion of the benefits of customer/vendor alliances and partnerships and how to eliminate non-value-added activities throughout the supply chain to radically decrease cost and cycle time and improve quality. We will look specifically at two major reengineering efforts underway to dramatically improve the performance of the order fulfillment process and the goods acquisition process. We will conclude that the key to quality improvement and cost reduction in the Age of Systems of the 1990's is to simplify business processes and reduce cycle time. This paper will describe how to use the TQM umbrella to effect this change.
Deepwater Field Development Options For The Campeche Bay
Authors: Barrere Rafael Martinez
Published: December 2007

The Campeche Bay is located in the Gulf of Mexico Continental Slope with an average of 80 Km from the coast in front of Tabasco and Campeche states, where the most prolific reservoirs of Mexico are. Oil production in this area had represented for Pemex Exploracion y Produccion (PEP), one of the most important experiences. As a result, we had a great production structure in shallow waters with a wide experience in the usage of fixed platforms. The offshore drilling exploration activities, leaded by PEP in the recent years have allowed to find an important amount of reserves located in deeper continental slope water. For that reason we decided to make a research about the field development options for six different deepwater fields placed in water depths from 200 to 700 meters in this area. These fields are representative of various deepwater prospects that had been identified.

The objective of this study is to define the technology that is available to develop deepwater fields in this area, and to identity the scenarios that are technically and economically feasible to develop each one of those fields. The study covers all aspects of the development, throughout the life of the field. This involves a broad range of technology aspects, including drilling, production platforms, processing systems and subsea production equipment.

Introduction

The experience reached in offshore development oil fields in Mexico, began in the early 60's with the Tiburon, Atun, Bagre, Marsopa, Escualo and Arenque fields exploration and exploitation which were located in shallow waters in front of the coast of the state of Veracruz at the North of the Gulf of Mexico.

Later on, it kept on studying the Gulf of Mexico Continental Slope, giving as a result the discovery of important oil fields on the west coast of the "Peninsula de Yucatan", what today is known as 'The Campeche Bay'.

Since 1978 the exploitation of oil fields located in shallow water in water depths from 16 to 78 meters were started. Nowadays PEP has more than 100 installed platforms including several production facilities. This has permitted the establishment of the mechanisms and strategies for going into deepwater oil field developments.

PEP through the Instituto Mexicano del Petroleo (IMP) has developed the needed infrastructure to face the goals of the efficient development of its hydrocarbons reservoirs, for this reason PEP & IMP have leaded the personnel training on different specialties on a master degree basis in Universities and Institutes well known all over the world.

Also, courses and seminaries like submarine systems, floating production systems, risers and mooring systems have been organized in Mexico imparted by University professors and high education institutes, as well as different international specialists suppliers.

PEP & IMP have also participated in several joint venture studies with international companies such as:

P. 1
Importance of a Methodology to Evaluate Technology of Remotely Operated Vehicles ROV's for Deep Waters
Authors: Manrique M. S. , Niño M. S.
Published: December 2007

International Petroleum Industry has invaded deep water for oil and gas exploitation, Pemex has also started plans towards this objetive however, at this moment Pemex is studying deep waters technology, but in the near future will require it.

An important point is that maintenance activities in deep water can not be carried out by divers.

Therefore remotely operated vehicles are necessary. Since ROV's technology is complicated it is important to have a methodology to evaluation in order to make the best decisions in the selection and buying process.

This paper is interesting, because shows the main parameters to be consider, problems, methods and procedures for ROV's technology evaluation.
Experiences With High Energy Stimulations for Enhancing Near-Wellbore Conductivity
Authors: Snider P. M. , Hall F. R. , Whisonant R. J.
Published: December 2007

During the past three years, Marathon has utilized a variety of "high energy" stimulation techniques on approximately 150 wells to enhance near-wellbore conductivity. The majority of these high energy stimulation treatments have been conducted in naturally fractured limestone and sandstone intervals. A number of specialized tools to improve field operations have also been developed. The high energy stimulations utilize pressurized gas (usually nitrogen), to inject various fluid systems into the formation. These fluid systems have included clear liquids (such as acids and alcohols) and fluids containing proppants to scour and prop the created fractures. High viscosity fluids containing proppants were overbalance surged into the formation in some applications. A tubing conveyed perforating (TCP)/ proppant carrier system was developed, allowing release of proppant into the fluid stream at the instant of detonation. Typical overbalance surge pressure gradients are 1.5 – 2.0 psi/foot; however, some wells have been stimulated at pressure gradients in excess of six psi/foot.

The paper will also discuss the results of directional radioactive tracer logs that were run to determine the number of fracture planes created with these high energy stimulations. A listing of some recommended types of data acquisition and key operational recommendations are included in this paper.
A New Rock Strength Model and Its Practical Applications
Authors: Gavito Daniel Garcia
Published: December 2007

SPE Member

The development of a new model to predict rock strength in-situ conditions is presented in this paper. This model was obtained using experimental triaxial compression data for limestones, sandstones and shales under confining pressure conditions up to 16,000 psi. A non-linear Mohr failure envelope is considered for rock strength under triaxial pressure conditions. Results of wellbore stability analysis using several failure models are presented and comparisons are made. Rock porosity is also included in the computational procedure through correlations of this parameter with the log-derived uniaxial compressive strength of the rock. The correlations developed are also applicable for proper rock bit selection.

Introduction

Field evaluation of rock strength in-situ conditions is fundamental in today's drilling engineering. Knowledge of rock failure behavior as a function of rock type, porosity; and triaxial stresses would provide information required to properly establish wellbore stability and optimum rock bit type selection, among others. This information is critical during offshore well planning and often is a contributing factor to the successful drilling of directional, highly inclined and horizontal wells.

P. 1
First Deep Core Taken Provides the Desired Results – Mexico
Authors: Ortiz Blas , Diaz Ernesto Quiroz , Garcia Leonardo Martinez , Salinas Juan Gaspar
Published: December 2007

Results of record-setting deep core operation in the southern region of Mexico by PEMEX Exploration and Production showed that efficient deep core recovery-is possible in a difficult formation, even at depths exceeding 22,000 ft (6700m).

The complexity of coring limestone can involve such problems as coring jamming, which lowers recovery ratios. In addition, limestone may have fractures which can complicate core recover/ by causing jamming or restricting entrance of the core into the inner barrel.

However, in this instance, a 97% core recovery rate was obtained using a conventional 4-3/4" coring assembly with aluminum inner tubes, and a 5-7/8" × 2-3/4" natural diamond core head.

Performance data, operational details, and economic analysis concerning use of this type of coring assembly is presented. The data describes the overall success of coring performance in limestone at extreme depths.
The Mexican Natural Gas Policy: A Limited Opening with an Increase in Production
Authors: Rodriguez-Padilla V.
Published: December 2007

Mexico's new development and modernization strategy for the natural gas industry and market is based on two pillars: public and private investment. PEMEX, a public organism, is responsible for upstream development, whereas the private sector is in charge of downstream development. In view of macroeconomic constraints, PEMEX is currently facing difficulties in financing its activities. The government is thus discussing whether to authorize a partial opening in exploration and production activities through a special type of service contract. As for the private sector's participation in transport, storage and distribution, there are still institutional, regulatory, entreprenurial and legal questions pending that may delay or inhibit investments. PEMEX's performance is crucial for private capitals to set up and survive in the spaces that have been opened to them. Mexico's full integration to the North American natural gas market is advancing slowly since there is still a need for substantial changes in assets ownership. In any case, il is very likely Mexico will participate as a net exporter in the medium-and long-terms.
Injection of Dilute Alkaline Solutions to Improve the Recovery Factor in Oil-Wet Reservoirs
Authors: Arteaga-Cardona M. , Pineda-Muñoz A. , Islas-Juárez R.
Published: December 2007

An offshore Field A located at the Gulf of Mexico has shown a low recovery factor by primary production. The wettability was evaluated by the Amott method and it was found that the porous media is preferentially oil-wet.

Experimental work was undertaken in order to define the feasibility of injecting alkaline solutions to the field in order to improve the oil recovery. The purpose of these experiments was to produce surfactants in-situ to low the interfacial tension and also to react with the reservoir rock surface to modify the wettability of the porous media. The experimental work considered the injection of sea water and sodium hydroxide mixtures into cores from field A. Experimental cores were previously saturated with the field oil which has a density of 0.8928 gr/cm and an acid number of 1.2 mg KOH/gr oil. The alkaline solution was injected at the rate of 25 ml/hr in order to insure velocity displacements about one feet per day, and also reservoir conditions were achieved; displacement pressure of 1,500 psi and temperature of 100°C were kept constant.

The experimental results show that the oil recovery can be higher than 50% when the alkaline solution was injected as compared whith injection of sea water. The effect of the alkali concentration over the recovery factor is also analyzed.
Alkaline Surfactant Polymer Formulation for Saudi Arabian Carbonate Reservoirs
Authors: Al-Hashim H. S. , Obiora V. , Al-Yousef H. Y. , Fernandez F. , Nofal W.
Published: December 2007

This paper presents a systematic study to test the applicability of alkaline-surfactant-polymer (ASP) processes as an enhanced oil recovery method to Saudi Arabian carbonate reservoirs, with the objective of designing a cost-effective ASP slug.

To achieve this objective, several alkalis were first screened to test their compatibility with the injected sea water that has large quantities of divalent ions. Then surfactant-polymer, alkalis-surfactant, and alkalis-surfactant-polymer interactions at the reservoir temperature (90°C) were investigated. Static and dynamic adsorption of surfactant on reservoir carbonate rocks were also investigated at the same temperature. IFT measurements were also made between the slugs formulated and crude oil from the same reservoir. And finally core flooding tests were carried out using Arab-D carbonate core samples to test the effectiveness of the formulated slugs. Two surfactants were used, Triton X-102 and Ethoxylated sulfonate (Dodi-flood Β1083), and the polymer used was FLOCON 4800C.

The results of the compatibility tests showed that the ASP slug has to be prepared using a softened brine and be protected by pre- and after-flush softening brine slugs. Β1083 surfactant was found to be a promising candidate surfactant for the conditions of the Saudi Arabian carbonate reservoir. A combination of NaHCO3 and Na2CO3 was found to significantly reduce the adsorption level of Β1083 surfactant on carbonate rock at low surfactant concentrations (<1% by wt.). This is very desirable for formulation of a cost-effective ASP slug. Finally, the results of core flooding tests under reservoir conditions using the formulated ASP slugs on Arab-D carbonate core samples showed a promising additional oil recovery.
Design and Optimization of Low-Cost Chemical Flooding
Authors: Wu W. , Vaskas A. , Delshad M. , Pope G. A. , Sepehrnoori K.
Published: December 2007

The main challenge of chemical flooding at the prevailing low oil prices is to reduce the cost. A reservoir simulator was used to systematically study a sandstone reservoir typical of an onshore, light-oil field in the United States that is a candidate for improved oil recovery using chemical flooding. These simulation results were used with an economic model to optimize the design of a chemical flood using surfactant and polymer. Project profitability was found to vary significantly at different surfactant concentrations. The best results were for the case when low concentrations of both surfactant and polymer were simultaneously injected, which is sometimes referred to as low-tension polymer flooding. Sensitivity analysis on the optimum design showed that the most important economics variables were oil price, discount rate, operating cost and chemical prices. Different polymer concentrations, permeability field realizations, and vertical to horizontal permeability ratios were also included in the sensitivity analysis. The benefits of Monte Carlo simulation as a risk assessment technique for surfactant/polymer flooding are demonstrated. Our results show that the process of designing chemical flooding projects can be improved using realistic reservoir simulations, current technologies such as horizontal wells, and an economic approach to optimization.
Foam Application in North Sea Reservoirs, I: Design and Technical Support of Field Trials
Authors: Surguchev Leonid M. , Hanssen Jan Erik
Published: December 2007

This paper gives results quantifying the reservoir potential and evaluating the suitability of selected foam processes for North Sea field application, extending earlier generic studies [1] to specific reservoirs and wells. Treatment of high-GOR production wells against coning and cusping, and of WAG injectors to divert injectants to less well flooded zones are reported. A fully-featured reservoir simulator with an empirical foam option is used.

For producer treatments, the application of gas-blocking foam to delay gas breakthrough is found to compete favorably with isolation techniques such as cementing and polymer-gel treatments, and offer additional benefits of selective gas shut-off, easier removal and potentially deeper treatment. History matching and evaluation of a recent foam pilot was performed and the sensitivity of the foam process to reservoir and foam parameters evaluated. Against gas coning, a treatment radius of 10 m and a mobility reduction factor of 30 may in a favorable case be sufficient to delay gas breakthrough for of several months. However, in order to be effective against gas cusping, a foam must be stronger and oil-tolerant. For injectant diversion, foam application by alternate injection of foamer followed by gas was found to offer a significant potential of improving WAG process efficiency.

If properly applied, foam can reduce gas production and increase oil production. Gas mobility reduction factor, foam persistence, volume of foamer injected, and foamer adsorption are the most critical foam parameters, while the permeability contrast and degree of communication between layers or zones are the most important reservoir parameters.
Foam Application in North sea reservoirs, II: Efficient Selection of products for Field Use
Authors: Dalland Mariann , Hanssen Jan Erik
Published: December 2007

This paper explains the principles of systematic product screening and qualification and evaluates the influence of the various foam, process and experimental parameters on the reliability of product selection. Because foam properties depend on the mode of application as well as on the conditions, efficient selection of a suitable foaming agent for field application can be performed only if the problem to be remedied by foam is well defined.

In order to be cost-effective, product selection should proceed in stages, conducting the required experiments in each stage only on a limited number of candidate products that have shown promising results in previous stages. Three stages may be distinguished: (i) pre-screening, (ii) screening, and (iii) qualification.

Temperature, core length, core permeability, and the use of representative crude oil and brine were found to be critical parameters in screening of foams for GOR-control application. For the cases studied, using the actual hydrocarbon gas and reservoir pressure were less critical and can be avoided if the effect of high pressure on foamer solution properties is properly accounted for. Except for cases of strongly oil-wet reservoirs, the use of reservoir material may actually harm screening due to the limitations it imposes on core length and re-use of core material possibly contaminated by previously tested products.
Reconciliation of Differences in Miscible Hydrocarbon Gas Floods Using NMR
Authors: Bowers M. C. , Purkaple J. D. , Gregory M. D.
Published: December 2007

Tertiary miscible core flood experiments (Lab A) were initiated to determine residual oil saturations (Sorm) for a Permian aged limestone reservoir. Cores were collected from several wells located in different areas of the reservoir and Sorm values ranged from 5.3 to 6.6%PV. The gas floods were conducted above the MMP with a 50% methane gas. In a separate project, additional floods were conducted on a different set of cores from the same reservoir (Lab B). These experiments were conducted above the MMP with a 65% methane gas and the Sorm values ranged from 10.4 to 11.9%PV. These differences in displacement efficiency will significantly impact the economics of a field scale project. The experimental procedures were compared and the differences were not significant. NMR T2 measurements were conducted on both sets of cores to examine the porous microstructures. NMR T2 relaxation curves (from which T2α, T 21, T22 and pore size distributions were derived) were compiled for each core. The T2α relaxation times associated with Lab A samples were much smaller than those associated with Lab B (i.e. Lab A cores had a much smaller mean pore size). The pore size distributions associated with Lab A cores were multimodal while those associated with Lab B cores were unimodal. Therefore, the cores had very different porous microstructures. Most importantly, Sorm was strongly correlated with T21, T22 and T2α (r =0.98, 0.94 and 0.97, respectively). As pore size increased, Sorm increased. The larger pores were apparently associated with dominate flow paths which resulted in bypassing and less efficient displacement. Secondary gas floods were also conducted and a similar relationship was found.