bluuebunny/crossref_metadata_2025 huggingface dataset:
Best Practices in the Allocation, Commissioning, and Maintenance of Ultrasonic Gas Leak Detectors
Authors: Naranjo Edward , Neethling Gregory A.
Published: February 2011

Ultrasonic gas leak detection (UGLD) is gaining broader acceptance in the oil and gas industry as a means for detecting combustible gas leaks. UGLD responds to high pressure leaks by measuring the airborne ultrasound emitted, which when detected by the sensor, provides a measure that is proportional to the leak rate. A principal advantage of the technology is that it does not require gas to be transported to the detector and provides coverage for a relatively large area, up to 20 m in radius, suggesting UGLD is suitable for detecting gas releases in open, well ventilated sections of offshore platforms.

Despite such advantages, the location criteria and commissioning and routine maintenance procedures for UGLD are not as well understood as those for conventional gas detectors. A reason might be that UGLD requires the establishment of an ambient ultrasonic background noise level to decide the alarm level and assist with selection of optimal location, a requirement that has no parallel with point IR or catalytic sensors. Location of ultrasonic gas leak detectors is also based on identifying the potential sources of leaks and taking into account acoustic reflections and interferences caused by continuous or short timescale background ultrasonic noise.

Such newness might be enough to give a few would be users pause. They may believe that UGLD is for people with high technical competence or that mapping, commissioning, and maintenance are best left to UGLD equipment manufacturers. Experience by one of the authors of this monograph suggests the contrary. Ultrasonic gas leak detection, for its reliance on ultrasound as a proxy for a gas leak, is a simple concept to understand. Over the course of over 3,000 installations during the last 10 years, offshore platform personnel have developed best practices that reduce the time and cost required for installing and commissioning ultrasonic gas monitors and that ease the burden on maintenance. In this report, we examine several of these procedures and highlight the simplicity of installation and maintenance of this method of gas detection.
First Ever Multi-stage Proppant Fracturing on an Openhole Horizontal Gas Well in Deep Natural Fissure Volcanic Reservoir in West China
Authors: Zhang Jing , Zhou Yikai , Zhang Jianhua , Wang Yong , Liu Hai
Published: February 2011

The Kelameili Gas Field in the Western China is a deep, naturally-fissured volcanic formation. The lithology, with significant degree of heterogeneity, varies from granite to tuff and breccia, has a low matrix porosity ranging from 4 to 10% and a permeability ranging from 0.015 to 0.026 md, and up to 984 ft in gross thickness.

Due to this low permeability proppant fracturing has been considered necessary on the conventional vertical well completions. However, the presence of natural fissures in the reservoir has often lead to the premature screenout of many treatments, resulting in lower than expected production.

The multi-stage proppant fracturing of DXHW-1 is a milestone for the operator due to: 1) The very first and the deepest horizontal well in a volcanic formation in China, been stimulated with a multi-stage proppant fracturing treatment; 2) The completion tubular and tools were designed for bottomhole pressure (BHP) up to 13,000 psi, and deepest coiled tubing (CT) cleanout (at 14,426 ft) was planned as contingency for any premature screenout.

This horizontal well was completed in five individual stages that were pumped continuously, one after the other, into the 2,454 ft openhole section using nine openhole isolation-packers. 341,270 lbs of 30/50 ceramic proppant was successfully placed into the formation, using a total of 7,981 bbls fracturing fluid. The well produced 35.3 MMscfd initially after the treatment and the production was stabilized at 17.65 MMscfd with wellhead pressure of 4,206 psi, which is four times higher than the average offset well.

The success of this treatment has supplemented additional 30% volume to the first gas station just from this single well, and also allows the operator to announce the discovery of an additional 3,637.4 billion ft3 of natural gas reserves in this field. Based on this success same completion model will now be used on future wells in the Kelameili Gas Field with several wells currently being planned.
LNG for Petroleum Engineers
Authors: Choi Michael S.
Published: February 2011

While remote parts of the world are awash with hundreds of trillions of cubic feet (Tcf) of natural gas, the industrialized West and emerging economies of the East can't get enough of the clean-burning, environmentally friendly fuel. The problem is transporting this compressible fluid long distances, across major bodies of water. For markets greater than 1,500 miles, liquefied natural gas (LNG) has proved to be the most economic option. By refrigerating natural gas (primarily methane) to -260°F (-162°C), thereby shrinking its volume by 600:1, LNG can be transported in large insulated cryogenic tankers at reasonable cost.

Natural gas liquefaction is a series of refrigeration systems similar to the air conditioning system in our homes consisting of a compressor, condenser and evaporator to chill and condense the gas. The difference is in the scale and magnitude of the refrigeration. A typical single-train LNG plant may cost $1.5 billion and consume 6-8% of the inlet gas as fuel. Since many of the impurities (water vapor, carbon dioxide, hydrogen sulfide, etc.) and heavier hydrocarbon compounds in natural gas will freeze at LNG temperatures, they must first be removed, and disposed or marketed as separate products.

This paper will provide an overview of LNG liquefaction facilities, from inlet gas receiving to LNG storage and loading.

However, the focus is on the liquefaction process and equipment. Differences among the commercially available liquefaction processes (cascade, single mixed refrigerant, propane-pre-cooled mixed refrigerant, double mixed refrigerant, nitrogen, etc.) will be discussed. The aim is to provide SPE members with a clear understanding of the technologies, equipment and process choices required for a successful LNG project.
Optimizing in Four Steps Composite Lost-Circulation Pills Without Knowing Loss Zone Width
Authors: Kefi Slaheddine , Lee Jesse C. , Shindgikar Nikhil Dilip , Brunet-Cambus Chrystel , Vidick Benoit , Diaz Nelson Ivan
Published: February 2011

A composite blend for controlling lost circulation has been developed on the base of a new four-step methodology. This blend exhibits superior performance over conventional treatments and eliminates missing loss-zone diagnosis and characterization.

Fighting lost circulation is a costly and time-consuming process. Conventional lost-circulation treatments try minimizing excess costs from rig time and fluid loss. In addition, they try avoiding the need for additional casing. However, these treatments are often based on trial and error without any practical technique to properly diagnose and characterize the loss- zone.

The new methodology addresses these shortcomings. The methodology proceeds in four steps: Dispersing a composite lost circulation material in a base fluid, Bridging the loss zone with fibers, Plugging the fiber networks, and Sustaining the plugs. Each step is parameterized by criteria, which can be optimized to meet the performance requirements. The fibers must possess certain form factor and exhibit specific physical properties to bridge open fractures after deploying through bottomhole assembly and drill bits. The composite plug also must endure pressure fluctuation during drilling or cementing and must tolerate erosion forces exerted by the fluid flow and downhole hardware. The four-step methodology provides an engineered combination of sized granules, stiff and flexible fibers. This new composite system was validated in several field trials in South America and Europe. In addition to the field trial results, this paper also describes the laboratory-scale and yard-scale tests, which were used for developing the new system. These tests helped establish guidelines for deployment through bottomhole assembly and drill bit.

These examples demonstrate that the novel composite blend system improves performance and robustness in curing losses compared with conventional single-fiber systems.
Demonstrating CO2 Sequestration as Part of a First Year Engineering Course
Authors: Neal P. R. , Ho M. , Fimbres-Weihs G. , Hussain F. , Cinar Y.
Published: February 2011

All engineering freshman at the University of New South Wales (UNSW) are required to complete the course "Engineering Design and Innovation". The course, commenced in 2006, provides students with learning opportunities in design, communication and teamwork. Each year, over 1,000 students combine lectures in design theory and communications skills with a hands-on design project. Ten of the schools in the Faculty of Engineering offer design projects as part of the course. The first project offered by the School of Petroleum Engineering was involved designing a "mini sucker rod pump". In recent years the School offers a project on CO2 sequestration - which has broader appeal and relevance to students across the faculty. Despite students’ enthusiasm to win the design contest, the aim of the course is to build skills rather than a device.

In this paper, we highlight the innovative approaches to demonstrating CO2 injection taken by UNSW first year students. We also evaluate the teaching and learning outcomes from this project. All teams worked together to design and build their device and to document their experience. However, some teams collaborated more effectively than others. We quantified this effectiveness using an online peer assessment tool that enables students to rate the performance of their team mates. We incorporated these ratings into the assignment of individual marks for group assignments.

We analyse the marks students achieved for various assessments and components of the course. We find that female students tended to out-perform their peers in both individual and team assessments. We also find that students who did well in individual components of the course also did well in the team components. We find it is hard to use early assessments to predict performance in later assessments. There is a strong connection between students’ results for their Design Proposal and their results for the Final Design work. We are able to show a statistically significant improvement for marks for presentations but not for report writing. We also found that there is an improving trend in marks over the semester. Having surveyed students, we find that 90% of students were satisfied with their experience of the course. Students found this course to be challenging and fun, giving them a good start in developing their skills as engineers.
Effect of Fracture Orientation on Induction Logs: A Modeling Study
Authors: Hu G. , Geldmacher I. M. , Liu R. C.
Published: February 2011

A common difficulty associated with fracture modeling is the need for a very fine mesh to simulate the detailed geometry of the fracture. Such a fine discretization in the 3D numerical model leads to a lengthy computation time; with tilting fractures complicating the problem further. In our work, we apply a novel technique that has recently been used in modeling non-conducting membranes in biological studies. This technique makes it practical to model even very thin fracture apertures.

The response of induction tools to fractures has been of interest to the oil industry for decades. Fractures are important indicators of formation characteristics. Several recent papers (Xue, et al., 2008 and Tang, et al., 2006) address vertical fractures intersecting a borehole wall in which the induction tool response was numerically simulated with 3D Finite Difference or Finite Element methods. However, in the cited publications, only vertical fractures were studied. In nature, fractures are not necessarily vertical and the wellbore can have an arbitrary inclination with respect to the fracture. The effect of fracture orientation therefore needs to be understood since it pertains to the nature of the fracture and the characteristics of the formation of interest. The innovative 3D Finite Difference simulation developed in this work reduces the size of the solution domain significantly and overcomes the challenge of geometry modeling in dipping, finite-length fractures. These breakthroughs allow us to look into the dipping effect of thin fractures accurately and efficiently. We look at the effect of a fracture with respect to dipping angle, fracture resistivity, aperture and length. As a result, we discuss the complications in the interpretation of induction logs influenced by fractures intersecting the borehole, both vertically and non-vertically.
Integrating Flow Simulation With Multi-Component Time-Lapse Seismic: Application to Postle Field CO2 EOR Project
Authors: Heris A. E. , Kazemi H. , Davis T. L. , Wehner S.
Published: February 2011

An improved understanding of flow behavior in older producing reservoirs, plus proactive reservoir management measures could lead to improving recovery efficiency. In this regard, one such measure is the use of time-lapse, multi-component seismic imaging to enhance the characterization of the reservoir's flow model. In this paper, we describe the application of this concept to a CO2 EOR project in Morrow sandstone in Postle field, Oklahoma, USA.

Production and injection in the Morrow sandstone will cause saturation changes and can influence reservoir pressure based on operating practices. These changes, in turn, affect acoustic and elastic properties of rocks, which are detectable by time-lapse seismic imaging. Coupling these changes into flow simulation improves our understanding of the reservoir heterogeneity and connectivity. A reservoir simulation model was initially built using available geological, petrophysical and engineering data. The fluid flow performance was compared against observed reservoir performance. Time-lapse seismic anomalies, which are indicative of permeability variation in the reservoir, have been used to better understand reservoir connectivity and improve the quality of the reservoir model. On the other hand, flow simulation results help geophysicists to better interpret the time-lapse seismic anomalies.

Results indicate that time-lapse seismic is capable of inferring the permeability field and can detect stratigraphic baffles in the reservoir. Additionally, it provides valuable inter-well information that can assist the history matching process and improve the quality of the reservoir model results. We also found out that although it is normally expected that the P-wave seismic anomalies show mainly the changes due to fluid saturation, our interpretation based on production / injection data and simulation study indicates that pressure changes can also affect the P-wave anomalies.

Our research results demonstrate that dynamic reservoir characterization and integration of flow simulation and 4D seismic is a viable method for building an integrated reservoir model that can be used to guide field operations and maximize recovery efficiency.
Pushing the Boundaries for Carbonate Productivity Estimations
Authors: Altunbay Mehmet , Bal Adrian , Bolle Luc
Published: February 2011

We propose a reliable methodology for evaluating and estimating productivity of carbonate reservoirs. Our methodology starts with a geological evaluation of image logs focused on locating fractures, quantifying the macro (vuggy) porosity and understanding the depositional and diagenetic environment. Porosity, below the image resolution, is partitioned by analyzing the acoustic and nuclear magnetic resonance (NMR) logs. These data are integrated with petrophysical evaluations by using conventional resistivity analysis conditioned with the fluid, pressure and mobility information gathered from a formation tester.

The crucial part of the analysis identifies vugs and their degree of connectivity using acoustic log, formation tester and NMR spectral data, which results in a p-factor. A reliable matrix permeability profile, responding to varying pore connectivity along the hole, is constructed by modifying the conventional NMR permeability with the p-factor. The modified matrix permeability profile is calibrated with the mobility data from the formation tester. Fracture identification and quantification of its permeability are achieved using Stoneley wave and NMR comparisons, and borehole image data. The resultant data set leads to productivity estimations by either handling fracture (if present) or matrix permeability in a dual permeability simulation or via a simple tank model. Timely estimations of carbonate reservoir productivity within weeks of data acquisition result in planning for appraisal or production wells and completion designs before SCAL results become available, early identification of test zones, and/or negating the need for production testing leading to sizable savings.
Equation-Of-State Modeling For Reservoir Fluid Samples Contaminated By Oil-Based Drilling Mud Using Contaminated Fluid PVT Data
Authors: Sah P. , Gurdial G. , Pedersen K. S. , Izwan H. , Ramli F.
Published: February 2011

Bottom-hole samples collected in well-bore systems using oil-based muds (OBMs) are likely to be contaminated by medium to heavy hydrocarbon fractions present in the OBM. PVT data measured for a contaminated fluid will not be representative for the clean reservoir fluid and such PVT data is hence often ignored by the operator, which means loss of a considerable investment. It would be valuable for the oil industry to have options for numerical cleaning of OBM contaminated reservoir fluids and to be able to carry out Equation of State (EOS) modeling and regression for a contaminated composition in a way that would allow PVT data for a contaminated fluid to be corrected to represent the uncontaminated fluid. This paper describes such a methodology, which is integrated with EOS modeling procedures for numerically cleaned reservoir fluid compositions. Thanks to this methodology PVT data for contaminated samples does not have to be ignored and oil & gas operators can justify investing in PVT analyses for contaminated fluid samples.

The paper details the process through which the available data can be utilized. The composition of the reservoir fluid is estimated from the composition of the fluid with a certain content of OBM contaminate. A regression procedure is afterwards applied using the available PVT data in order to ultimately develop an EOS model for the clean reservoir fluid. Compositional data and PVT data are presented for a real reservoir fluid contaminated with OBM. Since also data is available for the clean reservoir fluid, it has been possible to verify the validity of the suggested procedure. The numerical cleaning procedure does not require any non-standard laboratory data and the given method is also not restricted to any particular brand of OBM or well-type.
Electron Beam E-Beam Irradiation Improves Conventional Heavy-Oil Upgrading
Authors: Yang D. , Kim J. , Silva C. F. , Barrufet M. A. , Moreira R.
Published: February 2011

This paper presents the experimental and simulation study of E-Beam hydrocarbon upgrading process which shows the efficiency of E-Beam process and radiation energy transfer mechanism for single and multiphase fluid. Society's growing demands for energy results in rapid increase in oil consumption and motivates conversion of unconventional resources to conventional resources. There are enormous amounts of heavy oil reserves in the world but the lack of cost effective technologies either for extraction, transportation, or refinery upgrading hinders the development of heavy oil reserves. The traditional problem of conventional heavy oil upgrading is that it takes large amounts of thermal energy and expensive chemicals or catalysts to upgrade. Using E-Beam technology we may lower the energy requirement and reduce the use of specific chemicals or catalysts. The design of facilities can be simpler and will contribute to lowering the costs of transportation and processing of heavy oil and bitumen.
Probing Wettability Reversal in Carbonatic Rocks by Spatially-Resolved and Non-Resolved 1H-NMR Relaxation Analysis
Authors: Bortolotti V. , Macini P. , Mesini E. , Srisuriyachai Falan , Fantazzini P. , Gombia M.
Published: February 2011

The paper is addressed to help designing alkali/surfactant flooding Enhanced Oil Recovery methods. In particular, it has been verified that a polar interaction mechanism to change wettability of a carbonate rock from water-wet to oil-wet can be obtained by injecting adequate chemicals, and in particular a solution of oleic acid and non-polar oil, like dodecane used for laboratory experiments. It is worth recalling that wettability is a petrophysical property that directly affects oil recovery by controlling the location, flow and distribution of fluids inside the reservoir rock.

The study has been performed by combining spatially resolved and spatially non-resolved 1H-NMR (Nuclear Magnetic Resonance) information obtained on full-size cores (up to 7cm in diameter). In particular, spatially resolved quantitative NMR imaging maps (or Quantitative Relaxation Tomography, QRT) and spatially-non resolved (or Magnetic Resonance Relaxometry, MRR) analyses have been performed on full-size cores to track the process and to assess the quality of wettability reversal. Changes of relaxation time distributions and of T1 maps obtained in the experiments seem correlated with wettability changes measured after the chemical treatment, i.e., the contamination with a solution of oleic acid and dodecane. Although further investigations are needed, the combination of MRR and QRT seems a promising technique to correlate the traditional Amott wettability index with local values of T1 in internal sections of a rock sample.

In particular, the paper deals with the assessment and monitoring of wettability reversal of carbonate rocks used in laboratory studies to evaluate the efficiency of chemical Enhanced Oil Recovery methods, and in particular of alkali/surfactant flooding. The combination of 1H-NMR relaxation analysis, characterized by high temporal resolution, with quantitative maps, characterized by high spatial resolution, permits a better knowledge and the monitoring of the processes occurring inside the pore space leading to wettability reversal.
Geomechanical Assessments for Underground Gas Storage and CO2 Sequestration in Depleted Hydrocarbon Reservoirs
Authors: Fang Zhi , Khaksar Abbas
Published: February 2011

Depleted hydrocarbon reservoirs are attractive targets for gas storage and CO2 disposal because of proven storage capacity and seal integrity, existing infrastructure, etc. Optimum well completion and injection design in depleted reservoirs would require understanding of important rock mechanics issues such as: 1) drillability and completion of new wells, 2) maximum sustainable storage pressures avoiding fracturing and fault reactivations considering rock-fluid interaction effects. Building a field specific geomechanical model calibrated with well and production data is a pre-requisite for addressing these issues. Through a case study from a North Sea field, this paper demonstrates a systematic approach for geomechanical risk assessments for CO2 storage in depleted reservoirs.

A depleted gas reservoir at 4,265ft depth with current pressure of 45psi is considered in this study for CO2 sequestration. Historical well and production data are used for geomechanical modellings and defining the change of earth stresses associated with depletion and injection. Analyses show that because of the low fracture gradient within the depleted sandstone reservoir and the presence of non-depleted overburden shale, the inclination angle for new injectors should be kept below 50° to avoid hole failure or mud losses. Field data and analytical sanding evaluations indicate no sand control installation would be needed for injectors. Fracturing and faulting assessments confirm that the critical pressures for fault reactivation and fracturing of intact rocks are, far beyond the planned CO2 injection and storage pressures up to the original pressure 1,962 psi; hence no leakage due to faulting or fracturing is expected over the life of CO2 storage.

The methodology and overall workflow presented in this paper is expected to assist well engineers and geoscientists with geomechanical assessments for optimum well completion and injection design for gas and CO2 storage in depleted reservoirs.
Reserves Overbooking: The Problem We’re Finally Going to Talk About
Authors: Olsen Grant T. , John Lee W. , Blasingame Thomas A.
Published: February 2011

Oil and gas reserves estimates which honor disclosure requirements of the U.S. Securities and Exchange Commission (SEC) are critically important in the international oil and gas industry. Unfortunately, a number of E&P companies have allegedly overstated and subsequently written down certain reserves volumes in recent years. In some cases, the consequences have been quite adverse. We document some of these cases of reserves overstatements and summarize the consequences. Reserves write-downs are of obvious interest to numerous groups involved in the reserves estimation process and outcome, including estimators, managers, investors, creditors, and regulators. The magnitude and nature of recent overstatement cases, relative unfamiliarity with the SEC's inner-workings, and the Commission's new reserves reporting requirements, increase the need to examine critically reserves disclosures and reserves overstatements.
Drainage and Imbibition CO2/Brine Relative Permeability Curves at Reservoir Conditions for Carbonate Formations
Authors: Bennion D. Brant , Bachu Stefan
Published: February 2011

Proper modeling of the multiphase flow of supercritical CO2 in deep saline aquifers for CO2 sequestration (both cycles of drainage during injection and imbibition during CO2 migration) is critical in being able to understand and predict both the short and long term fate of the injected CO2 over extended time periods (hundreds to thousands of years). Current numerical models require the use of accurate two-phase CO2/brine relative permeability data at representative in-situ conditions in order to be able to accurately conduct these calculations. However, there are virtually no published data in the literature on the high temperature and pressure displacement character of CO2/brine systems in actual reservoir rocks, except for the data published by the authors in the June 2008 issue of the SPE Reservoir Evaluation and Engineering Journal. That data set, although it included a few carbonate cases, contained mostly measurements on clastic rocks. This paper presents a new set of nine relative permeability measurements (both drainage and imbibition) for carbonate rocks (limestone and dolomite) of higher permeability values than those in the initial work (which are thus more likely to be representative for candidates for CO2 sequestration in deep saline aquifers). The new data set to be presented includes also pre and post-test CAT-scan imaging of selected samples to illustrate potential effects of CO2 contact on potentially soluble carbonate matrices. The paper compares the new data set of measurements for carbonate rocks with the limited set of data available for carbonates from the previous work, and attempts to determine if specific relative permeability and residual saturation trends can be defined based on other rock characteristics that are easier to measure in routine core analyses, to allow extension of the data set to other carbonate facies elsewhere which have not been tested.
Has the Safety Case Failed?
Authors: Fitzgerald Brendan , Breen Paul , Patrick Joe
Published: February 2011

The paper examines the performance of the oil and gas industry, in particular in Australia and New Zealand, since the introduction of the Safety Case regime. Emphasis is placed on identified project issues and conclusions are drawn related to the current status of the industry, its maturity and its ability to apply the Safety Case regime in the manner required to achieve anticipated results. The paper examines whether issues that have led to project failings in recent years are inherent in the way the industry operates.

The paper discusses the experience of the offshore oil and gas industry in Australasia, in comparison with other parts of the world. The experience of other industries that apply the Safety Case approach is also discussed.

The core issue that is highlighted relates to the manner in which the Safety Case is applied, including issues of lack of understanding of the Safety Case process by management, the effect of contracting strategy on the effectiveness of the Safety Case and the lack of a common understanding of the role of the Safety Case. The paper is based on cumulative experience since the beginning of the Safety Case in the oil and gas industry, drawing in particular from experience on major projects within the last few years.

The paper highlights the manner in which the industry undertakes development projects, in particular, with some observations about the legacy that this leaves for the operating company and its personnel. More than 20 years after Piper Alpha, the industry has moved on and this paper seeks to provide a re-appraisal of the effectiveness with which major accident hazards and risks are managed.

The paper also seeks to draw conclusions that illustrate a way forward for the oil and gas industry.
An Intergrated Analytical Method in Identifying the Remain Potential of Thin Bed Reservoir on Deltaic System, Sengata Field
Authors: Demak Riswan Kiay , Alkaff Mohamad Hafiz , Ira Yashinta , Prasetiyanto Febri
Published: February 2011

This paper presents an integrated and simplified method with some field cases that can be applied to delay rapid production depletion and it focuses on the occurrences of the potential bypassed oil zone. The method that we used in here is by combining geological approach, with reservoir production history map as a result of data obtained during infill drilling and subsequent well work activities in the wells in the aim to get the remaining potential of reservoir. The primary benefit is to extent the field life as long as possible before it become a Marginal Field.

Well services are the common ways in maintaining production in every field, in this case Sengata Field. This aging onshore field has been developed by PT PERTAMINA EP since 1973 and the production reached its peak of 6000 BOPD in 1979 and with average decline rate of 60%, the field is on a fast declining trend. Like many other deltaic environment reservoirs in the world, the structures of this field is extremely sophisticated and consist of large number of reservoirs and most of them are thin bed reservoir and multiple stacked channels that contain oil, gas and formation water. The observed drive mechanisms consists of a combination of Solution Gas Drive and Water Drive The complicated geometry is a serious challenge for engineers who are responsible for determining lateral and vertical communication between the individual sand units.

Recent analytical method has been proven very successful in sustaining and revitalizing production shown by the oil increment up to 110% for it's target and allows PERTAMINA EP to optimize and prolong the field life.
Case History: Overcoming the Challenges of Deepwater Gravel Packing by Using Viscoelastic Fluids in Wells with Concentric-Annulus Completions
Authors: Joseph Kevin Peter , Cawiezel Kay E. , Wood Neil
Published: February 2011

Viscoelastic Surfactant (VES) Fluid technology was applied in the gravel packing of 18 deviated open-hole wells, having concentric annular completions, in Deepwater offshore India, with excellent results. The formation is unconsolidated, friable and highly permeable with very little margin between pore pressures, wellbore breakout pressures and fracture pressures. A preperforated liner was placed in the under-reamed open-hole section to protect against wellbore instability, and the sand control screens were landed inside the liner forming a dual annuli or concentric annulus, which was then gravel packed. Conventional gravel packing strategy suggests manipulating pump rates to minimize downhole pressures. However, with VES fluids, surface and bottom-hole treating pressures are easily kept to a minimum until screenout. This paper summarizes the challenges encountered; lessons learned and highlights the key advantages of the viscoelastic fluid systems used in these applications. The superior proppant-carrying capabilities of the viscoelastic system was proven showing higher success rates in complete packing of the open-hole sections compared to wells gravel packed using HEC-viscosified fluids. This paper also includes the details of the laboratory development and optimization of the VES fluids for both formate and calcium chloride based gravel pack carrier fluids. This involved screening of possible viscoelastic surfactants by compatibility tests, VES fluid rheology tests, internal breaker tests for the specific well conditions and friction pressure tests. The VES fluids’ superior proppant carrying capabilities, friction reduction properties, cost effectiveness, and non-damaging effects were the key success factors in overcoming the gravel packing challenges. The lessons learned from this project can be utilized in similar deepwater or extended reach applications to assist in improving success rates in gravel packing long open-hole intervals.
Three-Phase Flows Simulation for Improving Design of Gravity Separation Vessels
Authors: Vilagines Régis D. , Akhras Abdul Rahman
Published: February 2011

Computer simulation of gas/water/crude-oil flows inside gravity separators was developed. A three-dimension Eulerian model is used to describe flow features, including liquid free-surface, phase-mixing and droplets settling.

The simulations were conducted for a 45.5 meter long production trap operated in Saudi Arabia, required 105,000,000 mesh cells and ran on 93 parallel processors. The adjustment of the computation parameters and a technique to ensure constant liquid level in the vessel during the computation are described.

Density and velocity distributions in cross sections inside the vessel are presented and discussed.

The flow at nominal conditions was improved with a new inlet device. Computation results show how the inlet geometry effects propagate in the downstream flow, thus affecting the separation of phases.

Keywords: numerical simulation; separation; gravity; multiphase flow.
The Method and Expert System for Risk Assessment of Drilling In High-Sulfur Gas Field
Authors: Zang Yanbin , Wang Ruihe , Zhang Rui , Wang Zizhen , Li Xinzhi
Published: February 2011

The drilling operations had posed great potential threats to the surroundings and the safety of personnel, due to geological complications, lithological complexity, overpressure and acidic gas corrosion in high-sulfur gas fields. In order to accurately identify, evaluate and control the risks of drilling, the comprehensive evaluation index system (CEIS) and model for safe drilling based on fuzzy theory are constructed, and an expert system for drilling risk management is developed based on historical accident cases in high-sulfur gas fields.

The main structure of the expert system built in a framework way is introduced, and the operation principles of risk management by case reasoning for the expert system are discussed. Taking a drilling exploration area in the Northeast of Sichuan Basin as an example, the expert system is developed and then evaluates the drilling risk of Yuanba block. The results show that the comprehensive score of drilling security in YB-1 well is 0.559, which means very high drilling risks. In addition, the geological conditions and natural environment are identified as the two main potential factors that impact drilling security. All these evaluation results align well with the actual drilling practices, and this method of comprehensive evaluation for drilling risks is practical.

The evaluation method and expert system could provide a prime and valuable reference and conduction in rapidly locating the risk sources, accurately assessing drilling risks and improving the overall safety level of drilling.
Artificial Lift Using Impulse Pumping
Authors: Pierre B. , Gudmundsson J. S.
Published: February 2011

Impulse pumping is a new method for transport of fluids that can be applied in drilling and petroleum production. Of particular interest are applications of impulse pumping to artificial lift of liquids. In such situations, the motor driven part of an impulse pump appratus is located at wellhead; hence facilitating ease of operation and maintenance. In addition, no theoretical vertical lift limit applies in impulse pumping; thus simplifying design and applications of an impulse pump. Characteristic curves of impulse pumping first emphasize situations where impulse pumping performs with the greatest energy efficiency. Artificial lift of deep water for depressurization of the Statfjord field is then investigated. Operations, maintenance and performances of impulse pumping are then compared to those of electric submersible pumps and jet pumps based on results from three different industrial test cases.
Introduction of a New Logging While Drilling Resistivity Tool in the Liaoning Province of China
Authors: Lee Jonathan , Zhang Zhi Guo
Published: February 2011

The land drilling market in China has seen a significant increase in the use of gamma and propagation wave resistivity logging while drilling (LWD) tools in recent years, primarily through the offerings provided by major service companies. Although these technologies have been in use for many years, their availability to independent service companies has been restricted to either purchasing older generation tools from the majors or using their services at inflated prices, with limited resources to develop their own LWD technology. The authors describe the successful introduction of an LWD system within China by an independent service company working with an independent tool manufacturer―removing the reliance on technology developed by established international service companies.

The paper details the introduction of the formation evaluation technology and associated measurement while drilling (MWD) system by a local service company, established in wireline logging operations but new to the field of directional drilling, MWD and LWD. Focus will be placed on detailing a series of multilateral wells drilled within the Liaoning Province and the challenges faced with introducing new technology and interpreting data from high angle and horizontal wells.

The studies demonstrate the successful implementation of LWD technology in a field where previous attempts to log while drilling had failed. Through training provided by the tool manufacturer and use of field engineers with wireline logging backgrounds, the service company was able to log nearly 2200 m of lateral sections in the oil company’s most complicated multilateral project to date. The wells were drilled faster than previously with significantly improved system performance.

The availability to local service providers of a resistivity system with proven performance enables them to expand their service offerings without having to rely on technology provided by the majors―in turn allowing construction of more complex wells, designed to increase and optimize production.
Infill Drilling Potential in Tight Gas Reservoirs
Authors: Luo Shu , Kelkar Mohan
Published: February 2011

Many operators of tight gas reservoir fields are interested in determining the infill well potential in these fields. Over drilling may prove to be uneconomical; whereas, under drilling would leave unexplored reserves in the ground. In predicting EUR of a potential in fill well, the operator is interested in knowing what percentage of the production will be from incremental reserves (newly accessed) vs. acceleration reserves (which can be produced from existing wells). Higher the percentage of incremental reserves better is the potential of an in fill well.

In this paper, we present a novel method for determining the incremental vs. acceleration potential for in fill well in a tight gas reservoir. We evaluate the existing wells by plotting the data in a form so that the data can be linearly extrapolated. We predict the EUR for individual wells before and after new wells in the vicinity are drilled. By knowing how much gas is "diverted" from the older wells, we determine the acceleration component of an in fill well. By repeating the process as the field is being developed, we can determine the fraction of acceleration and incremental components of the EUR at each stage of infill drilling. We will also know how the EUR is changing as the well spacing is slowly reduced. To ensure our results are reasonable, we also compare our EUR values with EUR’s reported by the operator as proved reserves. Armed with this information, we can extrapolate in fill well potential for a smaller spacing, including the contribution due to acceleration vs. incremental production.

We developed this procedure for Wamsutter field in Wyoming. Using the procedure, we recommended in fill well locations to the operator. The comparison between actual data and the predicted results will be presented.
Planning and Execution of Highly Overbalanced Completions from a Floating Rig: The Ursa-Princess Waterflood Project
Authors: Stair Craig D. , Hinnant Chuck H. , Hines Natalya O. , Schober Jamie M. , Davis Chris L. , Lizak Ken F. , Pugh Brian A.
Published: February 2011

The Ursa-Princess Waterflood (UPWF) targets the Lower Yellow sand, the main reservoir in the Mars-Ursa basin in Mississippi Canyon, about 60 miles south of the mouth of the Mississippi river in the Gulf of Mexico, USA. The Lower Yellow sand, a world class Upper Miocene turbidite reservoir, has been on production in the Ursa and Princess fields since 1999, and has been drawn down nearly to the bubble point. The waterflood is intended to increase and stabilize reservoir pressure, and to improve sweep efficiency. To accomplish this, four subsea injectors were designed and constructed to inject treated seawater at some 40,000 bbl/day each for a target life of 30 years.

As the Lower Yellow reservoir was already highly depleted, unique risks were identified in the planned subsea completion operations, to be conducted from a Mobile Offshore Drilling Unit (MODU). Seawater, used as a completion fluid, was expected to be up to 4000 psi overbalanced to the reservoir, depending on the well location. This created the risk of either uncontrollable fluid level drop in the marine riser or extreme impairment to the sandface completion. In order to maintain well control with a fluid level at the surface and still deliver low skin completions, multiple design and procedural issues needed to be addressed, including:

Control systems on the rig and riser system to prevent uncontrollable fluid level drop, Perforating systems to minimize impairment in a high overbalance environment without adding undue risk to well control, Pill designs that could both control fluid loss at the sand face and clean up effectively, Downhole completion systems capable of functioning either under very high pressure differentials or against very high loss rates, Development of high burst screens that could withstand pilling in the event mechanical fluid loss devices failed.

As more Deepwater reservoirs approach depletion, specialized tools and procedures will be required to continue to deliver safe and effective sandface completions from floating rigs. This paper details many of these considerations, and summarizes the execution experience and results for one such reservoir.
Producing High CO2 Gas Content Reservoirs in Pertamina Indonesia Using Multi Stage Cryogenic Process
Authors: Suarsana I Putu
Published: February 2011

High CO2 reservoir gas in Pertamina is considered as unconventional gas reservoir since the gas has low heating value. The high concentration of CO2 in the gas caused the low heating. The gas need to be processed to make it marketable gas.

PERTAMINA has lots of sources of reservoir gas which content high CO2. The gas sources will be produced in the future since the gap of gas supply and demand in Indonesia is getting bigger mean while the hydrocarbon gas reservoir is diffucult to discover. There is no choice that the high CO2 gas content reservoirs will be produced in the future.

The high CO2 gas is considered as unconventional gas reservoir, corrosive gas, and unvaforable to be produced. High CO2 gas produced is not only has low calori but also will affect the global warming. In this case Pertamina has dilemma in producing the reservoirs.

In this paper will present about: alternative research about producing high CO2 gas content reservoirs. Determination of how to characterize reservoir fluids with high CO2 concen- trations for applications in compositional reservoir simulators.

Determination of separator conditions to obtain marketable gas by introducing a cooling process in a multistage separator.

A method to process high CO2 gas content to an environmentally friendly fuel gas which can eliminate the possible climate change caused by CO2.

Multi stage cryogenic process will separate CO2 gas reservoirs using cryogenic reservoir stage step by step. The number of stage will be define the effective pressure and temperature of the vessel to separate the CO2 from the gas reservoir. The Final goal is to obtain marketable gas which contain CO2 less than 10%mol, heating value more than 1000 btu/Mscf.
Gas Shale Reservoir Characterization: A North Africa Case
Authors: Chelini Valter , Muttoni Alda , Mele Maurizio , Rossi Elio , Galimberti Roberto , Ortenzi Andrea
Published: February 2011

In the last period with the rising price of oil and gas, the exploration and development of unconventional plays, that are already an economic reality in North America, are gaining more attention worldwide. It is common opinion that Gas Shale reservoirs are not peculiar only to the North America Basins. ENI E&P has focused attention on this type of unconventional reservoir, both in new countries and in the areas where it has historically been successful in conventional plays and where large amount of data are available.

New wells drilled in North Africa, planned to discover conventional hydrocarbon-bearing sandstone layers in the Silurian and Ordovician formations, have also been used to characterize in detail the Silurian Hot Shale that was normally interpreted as source rock. A dedicated data acquisition strategy was planned (logs and core) and, consequently, interpretation was carried out with the specific aim of characterizing this unconventional Gas Shale reservoir.

This paper documents the workflow used to characterize this unconventional reservoir.

It will examine in detail the wireline log interpretation based on integration with the experimental data from core. A robust characterization of a gas shale reservoir basically starts from core analysis (geochemical, petrographical, mineralogical and petrophysical) that are used for calibration and integrated in the wireline log interpretation. The benefits of these results will provide better evaluation of the hydrocarbon potential of Hot Shale in this area.