bluuebunny/crossref_metadata_2025 huggingface dataset:
Drill-Cutting Removal in a Horizontal Wellbore for Cementing
Authors: Ravi Krishna , Weber Lawrence
Published: December 2007

For effective zonal isolation, drill cuttings and gelled, dehydrated drilling fluid (GDDF) should be removed from the wellbore before a cement job, but such removal can be a challenge when the wellbore is deviated and the casing is not centered.

This paper discusses simulated wellbore experiments that investigated the effect of different factors on the removal of drill cuttings and GDDF from a horizontal well bore. The parameters studied included eccentricity, flow rate, hole size, casing size, fluids pumped as flush/spacer, and pipe movement.

The results showed that below a certain flow rate, the drill cuttings and GDDF could not be dislodged from the wellbore. In field applications, this flow rate must be known so that job designers can selectively design flushes that will effectively dislodge the drill cuttings and GDDF. As expected, eccentricity also alters the velocity profile in the narrow side of the annulus, and geometry was also a factor in removal efficiency.

The experimental setup, procedure, and results are discussed in detail. Flow rates needed to dislodge the drill cuttings and GDDF are also discussed, A numerical analysis of the fluid flow in wide and narrow annuli was also performed.

Introduction

Cement operators should always use the following guidelines to obtain a successful cementing job.Remove the drill cuttings.Remove the gelled and partially dehydrated drilling fluid. In some cases. this fluid will have the consistency of a paste. Hereafter, it will be referred to as partially dehydrated paste (PDP).Design the cement slurry to meet properties such as pumping time, fluid loss, gas migration, etc. In addition, design the density, rheology, and other placement parameters so that the cement slurry will displace the fluid ahead of it and seal the entire annulus. The cement formulation should also provide zonal isolation over the life of the well.

The removal of drill cuttings and PDP are influenced by the following:–properties of drilling fluid, fluid loss, plastic viscosity etc, a temperature, pressure, differential pressure across the formation–shutdown period–drilling fluid formulation–wellbore details–casing/drillpipe size–hole size–standoff/eccentricity–pore pressure–fracture gradient

For successful PDP removal, the downhole forces in both the narrow and wide sides of the annulus must exceed the yield stress of the PDP under downhole conditions. The force exerted could depend on the following factors:–flow rate of fluid–standoff/eccentricity–properties of fluid–pipe movement–wellbore geometry–scratchers

Although the general effect of these parameters on a cement job is well known, the designer must quantify the effect of each factor to optimize the design of each individual well. For a wellbore with a certain drilling fluid, geometry and standoff, it may be difficult to generate needed forces by hydraulic means only. In such cases, ways to reduce the downhole forces should be explored.

P. 347
The Planning and Drilling of a Wildcat Well in the Republic of Seychelles by an Operator-Contractor-Integrated Services Alliance
Authors: Marshall D. W. , Heenan D. H. , Reynolds J.
Published: December 2007

Constant Bank-1 is a 3,200m (10,500ft) wildcat well located in 50m (164ft) of water on a carbonate bank in the Republic of Seychelles, a group of tropical islands in the Indian Ocean.

This paper covers in detail how the contracting philosophy was developed to plan and execute the project through the formation of an alliance comprised of Operator, Drilling Contractor and Integrated Services Company. It examines the unique environmental and logistical features of this project and how the alliance sought to deal with these critical issues utilising the strengths of the respective companies to reduce risks and ensure a cost-effective, successful operation. The logistical management of planning a rank wildcat in a remote location with no practical means of resupply and no local resources was further complicated by anticipated technical difficulties with the well.

The paper concludes by considering the different objectives of each company in conjunction with the overall project objectives and how these respective goals were aligned to the mutual needs of the alliance. The lessons learned by all three alliance members are noted and recommendations made on how they would approach such an operation in the future.
Unique PDC Bit Configuration Dramatically Improves Hole Cleaning, Drilling Efficiency in Low Hydraulic Applications
Authors: Hertzler G. J. , Wankier J. T.
Published: December 2007

A new PDC bit design, which arose from a formal alliance between a contractor and bit manufacturer, has dramatically improved bit cleaning and overall drilling efficiency in applications where only low hydraulic horsepower is available. The new design has been run successfully in the Denver-Julesburg Basin of Colorado where the efficient operation of downhole mud motors places limitations on the standpipe pressure and flow rates of drilling rigs. These limitations require bits be run under very low hydraulic horsepower, which until recently made it difficult to optimize drill bit performance.

This paper describes the development of a multi-port PDC bit that has improved penetration rates, overall drilling efficiency and economics in applications with very limited hydraulic horsepower. The new design, featuring an undercut shank, a new cutting structure/nozzle configuration and durable carbide supported edge (CSE) cutters, has shown dramatic improvement in drilling efficiency, cost-per-foot and bit life. Individual bits employing the new configuration have drilled more than 200,000 ft, while on the average, the new design has increased penetration rates some 21% when compared to the M3 32 bit used previously. The design process and field performance will be presented and analyzed.

The new PDC design is effective in applications were high hydraulic horsepower is unavailable. It is especially beneficial in soft formations, where efficient bit cleaning is of paramount importance.
Mud Lubrication—A Viable Alternative in Well Control
Authors: Grace R. D. , Burton M. R.
Published: December 2007

It is common in drilling operations to experience an influx during a trip. Generally, the drill string is partially or completely out of the hole. Under these conditions, it is common for the influx to migrate to the surface while decisions are being made as to the proper procedures, or arrangements for equipment and services are being considered. In some instances, the drill string becomes plugged during a kick and it is not possible to circulate the influx out of the hole in the classical procedure.

In instances where trips are involved, the well is under control when the trip commenced and control is lost during the trip. In routine cases, control can be regained by merely circulating and replacing the influx with mud. In situations where the drill string becomes plugged, regaining control is slightly more complicated; however, the same technology can be used. Under these circumstances there are generally several alternatives.

One alternative is to lubricate mud into the hole and bleed the influx to the atmosphere. This procedure is not often used. A seat-of-the-pants approach can be disastrous and a technical approach is not well understood by most field personnel.
Slimhole Completion & Production – What To Do After We Drilled The Well?
Authors: Kroell E. , Spoerker H. F.
Published: December 2007

Slimhole technology recently has been established as a proven alternative to conventional drilling operations. Now that the drilling community has shown that slimhole can reach the objective and is both technically and economically feasible, completion and production aspects of small wellbores receive the focus of increased attention. This paper discusses influences of the drilling process on later production performance of the well and focuses on currently available completion systems. A critical comparison between conventional drilling systems and their formation damage potential with slimhole-specific characteristics is given. Questions concerning production and workover strategies that sometimes are considered to be a barrier when deciding whether to apply or reject slimhole technology are presented. Economic justifications for selecting slimhole solutions during the drilling phase pf the well are critically weighed against the impact of possible production impairments during the total well life cycle.
Placement Properties of Foams Versus Gelants When Used as Blocking Agents
Authors: Nimir H. B. , Seright R. S.
Published: December 2007

In this paper, we investigate whether foams can show placement properties that are superior to those of gels, when used as blocking agents. Specifically, we examine whether the concept of limiting capillary pressure can be exploited to form a persistent, low-mobility foam in high-permeability zones while preventing foam production and formation damage in low-permeability zones. Using a C14.16 α-olefin sulfonate, we measured mobilities of a nitrogen foam in cores with permeabilities from 7.5 to 900 md (750 psig back pressure, 104°F), with foam qualities ranging from 50% to 95%, and with Darcy velocities ranging from 0.5 to 100 ft/d. We also extensively studied the residual resistance factors provided during brine injection after foam placement. The results from our experimental studies were used during numerical analyses to establish whether foams can exhibit placement properties that are superior to those of gelants. This study found that compared with water-like gelants, the foam showed better placement properties when the permeabilities were 7.5 md or less in the low-permeability zones and 80 md or more in the high-permeability zones.
Development and Field Testing of a New Low Toxicity Polymer Crosslinking System
Authors: Moffitt P. D. , Moradi-Araghi A. , Ahmed I. , Janway V. R. , Young G. R.
Published: December 2007

A low toxicity polymer crosslinking system has been developed which is tolerant of high brine salinity and hardness and has worked well in two field applications. The system involves the gelation of polyacrylamide with zirconium lactate; this is a lower toxicity system than the commonly used chromium gelling systems. Microgels prepared with the new polyacrylamide/zirconium system have been tested in two different field applications: 1) an injection well test in a large waterflood unit in northeastern Oklahoma, the North Burbank Unit, and 2) an injection well and a production well test in a waterflood unit in northern Texas, the C. B. Long Unit. In the injection well test in the North Burbank Unit, 69,000 barrels of polyacrylamide/zirconium gel were injected into an injection well. Pressure falloff tests before and after polymer gelant injection showed a reduction in fluid mobility by a factor of 5 to 6 as a result of the crosslinked polymer treatment. In the C. B. Long Unit, an injection well was treated with 65,500 barrels of microgel and injection profile surveys before and after the treatment showed a diversion of 55 percent of the injected fluid to a low permeability zone. Several offset producing wells responded to the polyacrylamide/zirconium treatment and incremental oil production has been in the range of 15 to 20 BOPD. The production well treatment in the C. B. Long Unit resulted in a reduction of the producing water-oil ratio.

This low toxicity polymer crosslinking system has been developed for in-depth diversion of injection fluid in a variety of applications. The polymer gelant uses a fairly low concentration of polymer and zirconium crosslinker so large volume treatments are economical. The polymer system is also tolerant to hard brines and low pH environments.
Depositional Facies and Diagenetic History: Keys to Reservoir Porosity, Quality and Performance, East Vacuum Grayburg-San Andres Unit, Lea County, New Mexico
Authors: Siemers W. T. , Tisdale M. G. , Hallenbeck L. D. , Howard J. J. , Prezbindowski D. R.
Published: December 2007

The East Vacuum Grayburg-San Andres Unit (EVGSAU) is located in the Permian Basin, Lea County, New Mexico. The EVGSAU was unitized in 1978 and has been under waterflood operations since 1979. C02/water injection (WAG injection) commenced in 1986. An interdisciplinary reservoir study was initiated in 1994 to integrate the unit's geological character and reservoir performance in order to optimize the C02/waterflood. This paper examines the sedimentologic and stratigraphic framework, lithologic character, pore system, quality and continuity, and architecture and internal geometry of the reservoir and their application to safeguarding prime C02 flood performance within the reservoir.

The Permian-aged San Andres Formation is composed of two major, eustatically controlled, upward-shallowing carbonate ramp sequences that contain multiple, anhydritic, dolomitized successions in which subtidal grain-rich lithofacies grade upward into peritidal, mud-rich carbonates and siliciclastics. A siliciclastic, lowstand tidal flat unit, the Lovington sand, caps the lower sequence and separates the formation into the Lower and Upper San Andres. Grainstones and packstones deposited as high-energy shoals and bars are the primary reservoir lithologies. Diagenetic processes critical to the development of good reservoir porosity and quality are; (1) early dolomitization of the carbonate section, (2) intense dissolution and alteration of anhydrite to gypsum, and (3) dissolution of dolomite. Four correlatable subtidal grain-rich intervals constitute the chief flow units and the only continuous waterfloodable intervals across the field. Relationships between the distribution of the subtidal grain-rich lithofacies, porosity content, anhydrite and gypsum abundances, and structural position exhibit considerable potential for mapping reservoir flow units and for defining reservoir quality within flow units.

This geological model provided the architectural basis for the reservoir simulation pattern model used to evaluate reservoir performance and to modify EVGSAU operating plans to ensure optimum flooding. The geological model helped determine; 1) Upper San Andres vs. Lower San Andres performance, 2) infill spacing within the Upper and Lower San Andres, 3) the potential for horizontal injection in the Upper and Lower San Andres, and 4) repressurization volumes required for the Upper San Andres.
Exploratory Data Analysis of Production Data
Authors: Jansen F. E. , Kelkar M. G.
Published: December 2007

Production data represent a source of information about the ongoing dynamic flow process in the reservoir. A proper analysis of these data might therefore give an indication of the relationships governing the fluid flow. Exploratory data analysis is one tool which can be used to extract the required information and to establish a statistical significance to the results. This paper presents a simple approach to examine the interwell communication and interference of a mature waterflood in order to identify and rank areas of potential improvement. Using this as a screening process we can identify areas with the best potential for further and more detailed studies. In addition some of the problems and limitations associated with analysis of production data are discussed.
Numerical Simulation of Multimechanistic Gas-Water Flow in Fractured Reservoirs
Authors: Chawathe A. , Ertekin T. , Grader A.
Published: December 2007

A two-phase, two-dimensional, dual-porosity, dualpermeability simulator is developed to study the effects of multimechanistic flow of gas and water through tight, fractured reservoirs. The formulation incorporates the Newton-Raphson procedure to linearize the set of highly non-linear partial differential equations. These equations are then solved in a fully implicit form to obtain pressure and saturation distributions within the fracture network and the matrix.

In this paper, we discuss the development of the multi-mechanistic flow simulator with respect to fractured systems. For the multimechanistic systems, higher flowrates and cumulative production are seen at early times. This is attributed to the higher drawdowns experienced by such systems. At late times, a "choking effect" is hypothesized to be responsible for higher cumulative production from systems experiencing multimechanistic flow.
Implementing CO2 Floods: No More Delays!
Authors: Lambert M. R. , Marino S. D. , Anthony T. L. , Calvin M. W. , Gutierrez S. , Smith D. P.
Published: December 2007

The window of opportunity for maximizing oil profitability and recovery is closing for many fields in the Permian Basin. With this in mind, operators can not afford to continue delaying carbon dioxide (C02) enhanced oil recovery during this prolonged period of low and flat oil price. Key learnings from over twenty years of CO2 flooding are: the window of opportunity is closing,CO2 floods significantly increase oil recovery and extend the life of a field,when total costs (developing, operating, CO2 purchases and processing) are compared to drilling and acquiring for reserves, CO2 flooding is competitive,CO2 prices have declined commensurate with crude prices,CO2 technology and expertise have advanced,the cycle time from reservoir evaluation to flood installation is greatly reduced, andthe CO2 supply is more than adequate to recover all the possible tertiary reserves identified in the Permian Basin.

With many waterflood programs approaching the end of their economic lives, hundreds of millions of barrels of oil will never be recovered if tertiary recovery projects continue to be delayed. Proactive operators must reexamine the benefits of CO2 flooding now.
Design and Implementation of a Grass-Roots CO2 Project for the Bennett Ranch Unit
Authors: Hsu C. F. , Fitzgerald M. A. , Musallam S. C. , McCray T. L. , Purvis W. D.
Published: December 2007

Large-scale CO2 projects, like those implemented more than a decade ago in the Wasson Field, are not as attractive today because of large capital investments up-front and lower and uncertain oil prices. However, building upon our experience in large-scale floods, as well as recent improvements in the reservoir characterization and simulation technology, a grass-roots CO2 project can still be made attractive, in today's environment, by high-grading the reservoir resources, staging the development, and re-injecting the produced gas without facilitating a large gas processing plant. The paper contrasts the characteristics of the Bennett Ranch C02 project, a CO2 flood designed today, with traits of CO2 floods of yesteryear. The paper also highlights the innovative efforts in reducing and delaying the capital expenditures for wells and facilities, resulting in a less than 1 MM$ capital investment prior to the CO2 injection. Due to small flood patterns, significant production responses have been observed after only 3 months of CO2 injection.
Lost Soldier Tensleep CO2 Tertiary Project, Performance Case History; Bairoil, Wyoming
Authors: Brokmeyer R. J. , Borling D. C. , Pierson W. T.
Published: December 2007

The Lost Soldier Tensleep field tertiary performance has a noteworthy case history that demonstrates how an incremental 13% of original oil in place will be recovered from this sandstone reservoir using carbon dioxide. Located in south central Wyoming, the Lost Soldier Tensleep has been under carbon dioxide (C02) injection since 1989. From 1989 through 1995, a 61% hydrocarbon pore volume (HCPV) slug of C02 was injected into the reservoir to recover an incremental 13.6 million barrels of tertiary oil. Prior to C02 injection, the reservoir was producing 2,500 bopd at a 97% watercut. Within one year, oil production exceeded 10,000 bopd and is currently 6,000 bopd.

Since its start-up in 1989 with 47 producers and 40 injectors, the subject flood has used a water-altemating-gas (WAG) method and line drive pattern to process approximately 840 acres of reservoir. Illustrations of actual WAG injection cycles and resultant offset production response are included in this case history. The Lost Soldier flood has been so successful that one producing well had an incremental rate of 1700 bopd, carrying the unique distinction of having the highest peak incremental C02 response that the authors could find documented in U.S. literature.

Information contained in this paper provides observations and conclusions about field performance optimization as well as reservoir management philosophy. Several actions were completed during the early to mid-1990's to maximize recovery and profitability. These included maintaining miscible reservoir pressure, increasing natural gas liquid recovery, converting to sour reinjection, and exploiting downdip oil potential.
Pulsed-Neutron Capture Logging in Reservoir Management: Three Permian Basin Examples
Authors: Haynes F. M.
Published: December 2007

Pulsed-neutron capture logs (PNC) have been applied to address specific reservoir management issues in three mature Permian Basin fields (Cordona Lake, Cornell, and East Vealmoor). When combined with existing well data and a knowledge of formation fluid compositions, single runs with PNC logs have provided valuable reservoir surveillance data in secondary and tertiary recovery reservoirs. The logs have led directly to increased production, more cost effective workovers, and an improved understanding of fluid contact movement and injection breakthrough.
Areal Pattern Distribution of Remaining Oil Saturation in a Mature West Texas Waterflood – A Case History
Authors: Sharma Arun K. , Anil Kumar
Published: December 2007

A novel material balance technique presented by Kumar et al1 has been applied to estimate areal pattern distribution of remaining oil saturation, ROS, in a mature West Texas San Andres carbonate waterflood which is a potential candidate for the implementation of an improved oil recovery (IOR) project. This material balance accounts for two major dynamic unknowns: (1) loss of injected water vertically into non-target zones, and areally to adjacent patterns, and (2) progressive gas fill-up that begins with the start of water injection and may continue for several years before reaching the maximum fill-up.

The calculation procedure discussed here can be easily converted to a spreadsheet program and requires only readily available field production and injection data for oil, water and gas. The results indicate that 50 of the 103 patterns in the unit have been depleted to waterflood residual oil saturation, Sorw, and 33 patterns comprising 42% of the pore volume have relatively high ROS (>45%) even after 18 years of injection. A normal distribution in ROS is obtained in this unit with ROS ranging from a high of 67% to a low of 21%. This information is highly desirable for waterflood surveillance, monitoring, and in planning for an IOR project.
Multi-Lateral Horizontal Wells Optimizing a 5-Spot Waterflood
Authors: Hall S. D.
Published: December 2007

Interest in horizontal drilling has increased over the last six years. Most horizontal drilling has been in primary recovery operations to intersect fractures. Applying horizontal technology in a multi-layered carbonate waterflood has different challenges. For example, how can areal and vertical sweep efficiencies be improved? Short radius multi-lateral wells meet that challenge. Review of the design, application, and results shows multi-lateral wells superior to vertical and single lateral wells.
Comprehensive Evaluation of Horizontal Wells with Transverse Hydraulic Fractures in a Layered Multi-phase Reservoir
Authors: ElRafie E. A. , Wattenbarger R. A.
Published: December 2007

The objective of this work was to investigate the viability of converting existing conventional vertical wells to horizontal wells with multiple transverse fractures in targeted reservoirs. These reservoirs can be characterized as two thin, low permeability layers with no crossflow between them. The productivity of these reservoirs was very limited when producing by conventional vertical wells.

Reservoir simulation was used to evaluate various combinations of transverse fractures in horizontal wells. These results were compared with simulation results for conventional vertical wells, with and without vertical fractures. Only infinite conductivity fractures were considered. Early transient behavior as well as pseudosteady-state behavior were simulated.

The results show that horizontal wells with transverse fractures appear to make production of the targeted reservoirs economically feasible.

It has been shown that the productivity index of horizontal wells with transverse fractures is mainly affected by the distance between the outermost fractures and not by the number of fractures nor the spacing between them. Between fractures perforations has been shown to have negligible effects on increasing the productivity of horizontal wells with transverse fractures in these reservoirs. Decline type curves are presented, for horizontal wells with transverse fractures, for future performance prediction and reserves estimates.
An Engineer's Guide to Legal and Regulatory Matters for Horizontal Wells in Texas
Authors: Judah J. S.
Published: December 2007

This paper will provide a guide for engineers and operators to the legal issues, Railroad Commission's regulations and practices governing horizontal wells in Texas, with particular emphasis on their application in the Permian Basin. Horizontal drilling is standard in the Austin Chalk trend and its application is spreading as the technology becomes cheaper and gains acceptance. The paper will cover drilling issues, completions, allowables, secondary recovery, and land and legal considerations. Its purpose is to provide a practical map for Permian Basin engineers through the legal and regulatory minefield.
Characterization of the Naturally Fractured Spraberry Trend Shaly Sands Based on Core and Log Data
Authors: Banik Ashish K. , Schechter David S.
Published: December 2007

In this paper, the naturally fractured Spraberry Trend Area reservoirs have been characterized with emphasis on identification of oil-bearing silt and sands based on core-log correlation. Integration of extensive geological, geophysical and petrophysical data into a modem shaly-sand log interpretation model has been made in this study to characterize the Spraberry Trend properly. Quantitative cut-off criteria based on core-log correlation was developed which allows log based identification of thin oil-bearing intervals suitable for hydraulic fracture treatment. The Archie parameters (a, m and n) have been derived from core data to improve log-derived water saturation. Corederived porosity and water saturation have been compared with log-derived values for the purpose of quantitative identification of oil-bearing intervals. The results from this investigation provide recommendations for logging suites that will allow a better description of thin pay sands which characterize the Spraberry Trend throughout the Midland Basin. The methodology developed may be used primarily to understand the areal extent and pinch-off of productive intervals and the water saturation within the pay intervals. We believe this technique to be one of the ingredients required to understand the controlling parameter of fracture intensity within the pay zones (i.e. bed thickness, curvature etc).
Use of Production and Well Test Data with Predictive History Matching to Improve Reservoir Characterization for CO2 Flooding at the South Cowden Unit
Authors: Harpole K. J. , Gerard M. G. , Snow S. C. , Caldwell C. D.
Published: December 2007

The South Cowden Unit was selected for one of three mid-term field demonstration projects being conducted under the DOE Class II Oil Program for shallow-shelf carbonate reservoirs. The South Cowden project is designed to demonstrate the technical and economic viability of using horizontal CO2 injection wells and centralization of surface facilities to optimize CO2 project economics. If successful, this approach will help to improve the economic viability and application of CO2 flooding for many smaller fields which might otherwise soon face abandonment.

Successful design and implementation of the project requires a focused, cost-effective reservoir characterization effort to identify those reservoir characteristics and field areas best suited to application of this technology. Integration of production and well test data with geologic reservoir description information was necessary to develop a sufficient understanding of the permeability distribution at South Cowden. A predictive history matching approach was used in modeling historical field performance to further refine the reservoir description.
Fracture Monitoring Using "Low Cost" Passive Seismic
Authors: Taylor A. R. , Brown K. , Hinterlong G. , Watts G. , Zeitmann T. , Justice J. , Woerpel C.
Published: December 2007

Passive seismic measurements were taken before, during, and after a fracture stimulation treatment to monitor the fracture growth and optimize future fracture treatments. The seismic events created by the fracture treatment showed an asymmetrical east-west trend during the treatment, with wide variations in the locations of events. The passive seismic measurements support the previous belief that the fracture orientation for the field is east-west. However, the recorded events showed more complexity to the fracturing process than had been anticipated. The events showed a southwest trend toward a producing well along with the widely scattered events to the east. Neither, the 3D fracture simulator, pressure transient analysis, nor production injection data supports the very large fracture geometry of the passive seismic events.

Fracture lengths and heights from the passive seismic events varied along with the directions. The length of the wing to the southwest showed seismic events over 1200 feet from the well, while the east wing events only reached about 700 feet. The different wings also showed a large variation in the height of events. Although the treatment interval was 4820-4910 feet, seismic events occurred from 4550-4900 feet for the southwest wing and 4600-5008 feet for the east wing. The shorter length to the east is believed to be due to the well being offset to the east, by another injection well. The higher pore pressure, from the water injection, caused the fracture pressure to increase, thereby changing the direction of growth of the fracture.

The passive seismic results show that fully modeling the fracture process will need to incorporate a simulator that allows varying fracture parameters aerially as well as vertically. The 3D model, of the initial 1966 fracture treatment, showed a propped fracture length of 139 feet, with a propped area of 29,000 square feet. The prefracture falloff, which followed running a liner and a cement squeeze, showed an area of 15,000 square feet. The second 1995 treatment model results gave a length of 150 feet and an area of 26,000 square feet. The values for the last job match very closely the pressure transient results following the treatment, of 24,000 square feet, showing that the current model can predict fracture results adequately for most evaluation purposes. However, for nonuniform pressure gradients a more detailed areal model will be needed.
Digital Data Acquisition for Tracer Quality Control
Authors: McLaughlin James S.
Published: December 2007

Radioactive tracers have been successfully utilized to interpret the placement of stimulation treatments. A field data acquisition system has been developed to monitor tracer injection in real time. By placing a gamma ray sensor assembly over the stimulation line used in acid, fracture or cement treatments, radioactivity measurements are taken in order to monitor the amount and duration of the tracer being injected. An over the line monitor is connected to a laptop computer in order to record the data. This system insures that the tracer is added in a continuous, controlled manner as required. Software has been developed to enhance the ease of data acquisition in harsh field environments. The equipment is also capable of monitoring other stimulation treatment variables such as pressure and temperature. A description of the hardware and software is followed by several examples in the body of the report.
Benchmarking – A Catalyst for Operational Improvement in the Exploration and Production Industry
Authors: Hinn R. L.
Published: December 2007

Benchmarking has proven to be an important catalyst in the quest to attain significant cost reductions in Amoco's Permian E&P operations. Benchmarking results have been derived from both external and internal efforts. Each of these types of analysis produce a unique data set which can be utilized to foster positive change within an organization.
Percussion Drilling…Is It a Lost Technique? A Review.
Authors: Samuel G. Robello
Published: December 2007

This paper presents a review of the benefits and performance of downhole percussion hammers. The advancement of drilling technology and the extensive use of coiled tubing coupled with different downhole motors prompted another look at the percussion type of drills. Achieving very high extended reach wells also have necessitated a high axial driving mechanism. The potential benefits of the percussion type of drilling machine for future operations are given, supported by the performance of the tools. The use envelope and the benchmarks of the tools by different manufacturers down the years have been discussed. The hammers developed and operated have been supported by enough field runs to prove the sustainment of the tools. Different models of downhole hammers can be categorized as first generation tools which include the developments from early time to the development of Bassinger tools. The second generation tools from post-Bassinger to the recent developments are discussed broadly. The basic principle involved and the necessity to consider the correct stress waveform to simulate the performance of the downhole hammer energy transfer are reviewed.
Underbalanced Drilling, Praises and Perils
Authors: Bennion D. Brant , Thomas F. Brent , Bietz Ronald F. , Bennion Douglas W.
Published: December 2007

Underbalanced drilling has been utilized with increasing frequency to minimize problems associated with invasive formation damage which often greatly reduce the productivity of oil and gas reservoirs, particularly in open hole horizontal well applications. Underbalanceddrilling, when properly designed and executed, minimizes or eliminates problems associated with the invasion of particulate matter into the formation as well as a multitude of other problems such as adverse clay reactions, phase trapping, precipitation and emulsification which can be caused by the invasion of incompatible mud filtrates in an overbalanced condition. In many underbalanceddrilling operations, additional benefits are seen due to a reduction in drilling time, greater rates of penetration, increased bit life, a rapid indication of productive reservoir zones and the potential for dynamic flow testing while drilling.

Underbalanced drilling is not a solution to all formation damage problems. Damage due to poorly designed and/or executed underbalanced drilling programs can rival or even greatly exceed that which may occur using a well-designed conventional overbalanced drilling program. Potential downsides and damage mechanisms associated with underbalanced drilling will be discussed. These include: Increased cost and safety concerns.Difficulty in maintaining a continuously underbalanced condition (due to such factors as pipe connections in rotary drilling, bit trips, mud pulsed logging, bit jetting and flushing effects, localized depletion and subsequent repressurization effects, poor knowledge of initial reservoir pressure, multiple zones with differing initial pressures, slug flow and liquid holdup in the vertical section of the wellbore, frictional pressure drop and mechanical problems with surface equipment or gas supply sources).Spontaneous imbibition and countercurrent imbibition effects.Glazing, mashing and cuttings induced damage.Macroporosity gravity induced invasion.Difficulty of application in zones of extreme pressure and permeability.Political/career risk associated with championing a new and potentially risky technology.

This paper discusses reservoir parameters required to design an effective underbalanced or overbalanced drilling program, laboratory screening procedures to ascertain the effectiveness of underbalanced drilling in a specific application and presents screening criteria with respect to the types of reservoirs which present good applications for underbalanced drilling technology.
Continuous Improvement in Well Profiles and Bits Enables Permian Operator to Optimize Slim Hole Program
Authors: Tank W. , Pohler S. , Felderhoff F.
Published: December 2007

This paper describes the evolution of a slim-hole directional and horizontal drilling program in the Permian basin. The development and application of small-diameter roller cone bits has played an important role in the success of this program. The integration of these bits with specialized motors and fluid systems, has produced optimal well profiles which will be presented and analyzed. Case studies of Marathon wells showing significant per footage cost reductions, increased footage/penetration rate per bit and increased displacement will be presented.
Modeling of Pressure Buildup on a Kicking Well and Its Practical Application
Authors: Miska Stefan , Samuel G. Robello , Azar J. J.
Published: December 2007

This paper describes a new method for prediction of pore pressure and formation permeability from a kicking well. Getting reliable and accurate information about reservoir parameters (when the formation damage is minimal) is of critical importance for making proper well completion decisions. In addition, when a well kicks, inaccurate estimation of the formation pressure may cause loss of equipment and possibly the well and human lives. To combat the above problems, a conventional pressure analysis method is modified to predict the formation pore pressure and estimate directional formation permeabilities from a kicking well. The method is simple, and the only prerequisite is that the buildup data be collected upon shutting-in a kicking well. Examples of using simulated as well as actual field data, are provided to demonstrate the practical application of the method.
Problem Identification and Solution Method for Water Flow Problems
Authors: Pappas James , Creel Prentice , Crook Ron
Published: December 2007

In the past, it was difficult to justify the expense of water control because it often produced poor results. The most commonly used water-control technique, cement squeezing, had only a 50% success rate. Other more exotic treatments had even lower success rates and were performed only as experiments or "last resorts." These unsuccessful treatments often resulted because the source of the problem was not correctly identified. With the tools available today, the essential element of conformance control is identifying the nature and source of the problem. Once the problem is correctly identified, the best material or solution to solve this problem must be determined. The best placement technique must also be determined to ensure that the material or solution is placed where it has the best possible chance of solving the problem.

Addressing poor sweeps, channeling, interwell communi-cation, and other water-control problems is especially important in fields where injection is used to enhance oil production. Chemical analysis and water flow logging can help operators isolate water flow, invasion, and annular leaks that destroy casing integrity and decrease profitability. A case history in-volving five wells demonstrates the use of analytical techniques to identify conformance-control problems. It also focuses on the evaluation and solution processes. In essence, the case indicates the importance of thoroughness. In this case, identification, evaluation, implementation, post-analysis, and re-evaluation were combined into a single process.
On the Physics of Multimechanistic Gas-Water Flow in Fractured Reservoirs
Authors: Chawathé A. , Grader A. , Ertekin T.
Published: December 2007

Multimechanistic flow occurs in reservoirs when the fluid transport is influenced by both, pressure and concentration gradients. In this research, we investigate the dynamics of multimechanistic gas-water transport in fractured systems. To achieve this objective, we have developed a two-phase, two-dimensional dual-porosity, dual-permeability simulator. The details of the simulator development are presented in a previous paper (Chawathé et al., 1996).

Our studies indicate the presence of higher flowrates and cumulative production at early times in systems experiencing multimechanistic flow. This is attributed to the higher drawdowns experienced by such systems. At late times, a "choking effect" is hypothesized to be responsible for higher cumulative production. In this paper, we investigate the physics underlying this multimechanistic flow behavior. We do this by carefully analyzing a fractured system which clearly displays multimechanistic flow characteristics.
A Semi-Analytic p/z Rate-Time Relation for the Analysis and Prediction of Gas Well Performance
Authors: Ansah J. , Knowles R. S. , Blasingame T. A.
Published: December 2007

This paper presents a rigorous theoretical development of long term boundary-dominated flow solutions which involve direct coupling of the stabilized flow equation with the gas material balance equation. Due to the highly non-linear nature of the gas flow equation, pseudopressure and pseudotime functions have been used over the years for the analysis of production rate and cumulative production data. While the pseudopressure and pseudotime functions provide a rigorous linearization of the gas flow equation, these transformations do not provide direct solutions. In addition, the pseudotime function requires the average reservoir pressure history—which in most cases is simply not available.

Our approach uses functional models to relate the viscosity-compressibility product with the reservoir pressure (p/z) profile. These models provide approximate, but direct, solutions for modelling gas flow during the boundary-dominated flow period. For convenience, the solutions are presented in terms of dimensionless variables and expressed as type curve plots. Other products of this work are explicit relations for p/z and Gp(t). These solutions can be easily adapted for field applications such as rate prediction.

We also provide verification of our new flowrate and pressure solutions using numerical simulation results and we demonstrate the application of these solutions using a field example.
Potential Distribution Around Sources With Finite Length Horizontal and Vertical Partially Penetrating wells and Fractures Part I: Steady State Fluid Flow
Authors: Azar-Nejad F. , Tortike W. S. , Farouq Ali S. M.
Published: December 2007

The mechanism of fluid flow in the reservoir can be determined through the knowledge of the potential distribution inside the reservoir. Presenting Discrete Flux Element (DFE) Method this paper provides a general analytical solution to potential distribution due to a producer with straight or curvilinear configuration for both uniform flux and uniform potential inner boundary conditions in 3-D. The results consist of: 1) the equations for productivity indices, 2) shape of the drainage area for each case. This study shows that the drainage area for a horizontal well, beyond a certain radius is vertical in the vertical planes (xz and yz). In the horizontal planes it is first elliptical and at points far from the producer it is circular.
Applications of Azimuthal Anisotropy from Dipole Shear Sonic in Western Venezuela
Authors: Johnston L. K. , Campo O. , Lagoven S. A. , Viloria O.
Published: December 2007

Wellbore mechanical properties have long been used to model formation responses when planning highly deviated wells, horizontal wells and fracture treatments. Now, with the inclusion of the maximum stress direction and horizontal stress ratio, a complete model of the formation response to stress can be obtained.

The fact that shear waves will split and become polarized parallel and perpendicular to natural fractures is well documented. The fact that the fast shear wave is oriented in the direction of the maximum horizontal stress is also well documented. Cross dipole shear data from a digital sonic tool is processed to obtain oriented fast and slow shear waves. The theory of shear anisotropy processing is reviewed and the quality control and interpretation of the resulting anisotropy log are discussed.

For this case study, azimuthal anisotropy data obtained from dipole shear sonic logging in Western Venezuela is used to determine the direction of maximum horizontal stress and horizontal stress ratio. This information is then used to determine the oriented mechanical properties. These mechanical properties are presented in the form of an oriented wellbore stability analysis.

When the information obtained from dipole shear sonic anisotropy logging is used in the planning of horizontal wells, deviated wells and fracture treatments the overall cost of the well can be reduced. Using this information, efficiency can be increased and potential problems can be avoided.
The Contribution of Wellbore Imaging to Interval Selection in Naturally Fractured Reservoirs
Authors: Mendoza R. J.
Published: December 2007

The selection of intervals to be perforated in naturally fractured reservoirs is often aided by the use of wellbore images.

The current trend in several mexican fractured reservoirs is to include an analysis of wellbore images to define production intervals.

Visualization of the rock texture is also possible from images, and differentiation of secondary porosity types can be defined. Standard logging techniques to detect fractures do not distinguish betwen unconnected vugs and open natural fractures. In tight carbonate formations, hydrocarbon production comes mainly from these fractures.

Other data that can be obtained from the images are the orientation and frequency of fractures, their relationship with the reservoir structure and porosity, and their distribution.

This paper includes examples and correlations betwen producing intervals and wellbore images.
A New Practical Approach to Rotary Drilling Hydraulics
Authors: Scott Kenneth F.
Published: December 2007

This paper presents a simple, practical and accurate method of selecting jet bit nozzle sizes. Rather than calculating friction losses in the drilling system, a measure of total friction loss is taken from the standpipe and a graphical solution of pressure loss across the bit is subtracted from the standpipe reading, resulting in the actual measurement of system pressure losses. Drilling hydraulics are based pressure losses. Drilling hydraulics are based on maximum bit horsepower, hydraulic impact, or jet velocity and are all dependent on a predetermined friction loss in the system. predetermined friction loss in the system. This method may be used to maximize any one of the three.

Because mud properties and hole conditions change, nozzle size selection is made from data obtained prior to pulling a dull bit out of the hole. A work graph is presented, and typical field data are used in working example problems.

Introduction

The subject of rotary drilling hydraulics has received a great deal of attention in the literature. Excellent papers have been written by Bobo, Kendall and Goins, and Kelly. Recent trends have been to maximize bit hydraulic impact. Examples will be worked in this paper which will maximize hydraulic impact and bit horsepower.

The derivation of the maximum horsepower, impact force, and jet velocity equations are presented in an excellent paper by Kendall and presented in an excellent paper by Kendall and Goins.

Conditions that are necessary for maximizing any of these three parameters are listed without derivations in Table 1.

Graphs are presented for obtaining circulation rates for various pump liners, stroke length, and strokes Graphs 1A and 1B).

A nomograph of annular velocities-vs-circulation rates for various hole and drillpipe size combinations is presented (Graph 2).

The method for constructing the work graph from which nozzle sizes are selected is presented. Field examples are solved in the discussion.