bluuebunny/crossref_metadata_2025 huggingface dataset:
Coal Permeability and Its Behaviour with Gas Desorption, Pressure and Stress
Authors: Connell Luke D , Pan Zhejun , Lu Meng , Heryanto Deasy , Camilleri Michael
Published: February 2011

Coal permeability is sensitive to the effective stress and is therefore coupled to the geomechanical behaviour of the seam during gas migration. The geomechanical response of the seam is complicated by the additional effect of coal shrinkage with gas drainage. Existing coal permeability models, such as those proposed by Shi and Durucan (2004) and Palmer and Mansoori (1996), simplify the geomechanical processes by assuming uniaxial strain and constant vertical stress. Connell (2009) and Connell and Detournay (2009) investigated these assumptions using a fully coupled simulator. An important obstacle to the use of the coal permeability models of Shi-Durucan or Palmer-Mansoori is the characterisation of the various physical properties involved, since a number of difficult to measure properties are involved. This paper summarises the influences on coal permeability and in particular the role of coal shrinkage with gas desorption and compressibility with pore pressure and the importance these processes could have on predictions of gas production. The paper considers the assumptions involved in the derivation of the models to describe coal permeability and the impact these could have on predicting gas production. A novel model is derived which is more general and this serves as a basis for the discussion presented in this paper. Measurements of coal properties (cleat compressibility, geomechanical properties, Biot coefficient) with respect to pressure are presented for two Australian coals (a sample from the Hunter Valley and one from the Bowen basin) and the measured behaviour compared with that assumed in the Shi-Durucan and Palmer-Mansoori coal permeability models derivation.
Transforming Data into Knowledge using Data Mining Techniques: Application in Water Production Problem Diagnosis in Oil Wells
Authors: Rabiei M. , Gupta R. , Cheong Y. P. , Sanchez Soto G. A.
Published: February 2011

Excess water production is a serious economic and environmental problem in most mature oil fields. Accurate and timely diagnosis of the water production mechanism is critical in the success of the applied treatment methodology. While many empirical techniques have been traditionally used in production data analysis, the significance of water-oil ratio (WOR) in proper identification of the type of the water production problem in oil wells is not yet fully investigated. Data mining techniques could facilitate extracting any hidden predictive information from oil and water production data to be used in water control studies.

This paper applies a meta learning classification technique called Logistic Model Trees (LMT) to diagnose water production mechanisms based on WOR data and static reservoir parameters. Synthetic reservoir models are built to simulate excess water production due to coning, channeling and gravity segregated flows. Various cases are then generated by varying some of the input parameters in each model. A number of key features from plots of WOR against oil recovery factor are heuristically extracted by segmenting these plots at certain points. LMT classifiers are then applied to integrate these features with reservoir parameters to build classification models for predicting the water production mechanism in different scenarios of pre and post water-production stages.

It is observed that a valid association between WOR data and the water production mechanism exists. Our results with high prediction accuracy rates of 88% for pre-production and more than 94% for post-production stage demonstrate efficiency of the proposed LMT classifiers and significance of WOR values in classifying excess water production problems.
Assessing the Underground CO2 Storage Potential in a Highly Populated and Industrialized Area: The Case of Lombardia Region Italy
Authors: Macini P. , Mesini E. , Moia F. , Guandalini R. , Savoca D.
Published: February 2011

The paper is aimed to the assessment of the CO2 underground storage potential of Lombardia Region (Italy), one of the most populated and industrialized area of the Country. The study is intended to locate adequate sites for the potential application of carbon capture and geologic storage in deep underground formations.

The first part of the study concerns the evaluation and analysis of the mass of CO2 generated in Lombardia Region (the largest CO2 producer in Italy, with over 70 million metric tonnes per year of CO2 released in the atmosphere) by investigating both the localized sources (industry, power generation, etc.) and the diffused ones (transport, domestic heating, etc.). The second part of the study concerns the technical evaluation of the possibility to put into practice the geologic storage of CO2 in deep underground formations of Lombardia Region. Finally, the study reports some preliminary evaluation for the possible implementation of a CO2 storage pilot plant in the area. In particular, a potential candidate located in a deep saline aquifer has been identified, and its geological and hydrodynamic modelling has been extensively studied and analyzed. The investigated reservoir has a storage capacity of more than 370 million metric tonnes of CO2, corresponding to about 30 years of CO2emissions produced by the main thermoelectric power plants located in the same area.
Breaking Low Permeability Fracturing Myth – VICO Indonesia
Authors: Wijanarko Andre , Rylance Martin , Pizzolante Italo , Chatib Hazman , Dharma Budi
Published: February 2011

VICO Indonesia is the operator of the Sanga-Sanga Production Sharing Contract; located onshore of the Mahakam delta, in East Kalimantan, Indonesia. Since inception the PSC has produced over 70% of the estimated original gas in place. The fields are relatively mature with most of the remaining gas resources locked up within the lower permeability reservoirs, where conventional tight-gas completion approaches have not been very effective in ensuring depletion of the resource. A valuable prize of at least 0.5 TCF would be readily achievable, if these lower permeability resources could successfully be developed and recovered.

The lower permeability formations being referred to; are typically sub milli-darcy, and the ability to achieve any kind of sustainable economic production rate has been extremely problematic. Previous attempts at hydraulic fracturing within VICO, over nearly three decades, have been dramatically ineffective and have rarely enjoyed any sustained production improvement at all. Geologically the reservoirs are best described as distributary river channels, in a lower deltaic plain environment and therefore these individual sands can vary in size and connectivity quite substantially. Alternative technologies, such as horizontal drilling are being applied, but only within those sand bodies which are larger and which can therefore readily support the economics associated with horizontal well drilling.

In 2006 a detailed technical review of the previous 30 Years of hydraulic fracturing operations was commissioned, this review noted that there were five basic ‘skins’, which were causing problems for hydraulic fracturing. These ‘skins’ were: wellbore integrity, execution QA/QC, relative-permeability, regional tectonics and poro-elasticity. The data was extremely convincing and based upon the review a decision was made to implement a five well pilot in order to confirm the findings and present solutions.

This paper will describe the long and difficult journey of VICO hydraulic fracturing, from the original treatments through the recent review, the fracturing pilot from 2007 - 2009 and into the early stages of the new fracturing campaign planned for 2010 - 2012, The paper will present the results of the detailed study, the implementation phase of the pilot and the forward plan for the VICO low permeability zone(s) based upon the significant progress, successes and deliverables of the fracturing pilot in the Nilam G-Sands.
CO2 Storage in Saline Aquifers: Design of a Demonstration Project to Dispose CO2 Associated with Natural Gas Fields in South China Sea
Authors: Zhang L. , Ren S. R. , Zhang Y. , Mi H. G. , Ma Y. X.
Published: February 2011

DF1-1 gas field in the west of the South China Sea is associated with high concentration of CO2. Many options have been assessed by the operator (CNOOC) in recent years in order to dispose the CO2 separated from the gas stream. In this study, geological storage of CO2 into offshore saline aquifers near the gas separation plant on the Hainan Island is considered, and a demonstration project is proposed and designed in terms of aquifer selection and assessment, CO2 transportation and injection, and project economics. Several aquifer structures around the gas field and near the Hainan Island were investigated and assessed with respect to geological structure, reservoir and trap features, fluid properties, storage capacity and site location. A saline aquifer (namely LT13-1), 60 km offshore the Hainan Island, was chosen as the storage site. CO2 will be transported by a long-distance subsea pipeline at high pressure and injected into the aquifer via a subsea well-head and through a horizontal well. Reservoir simulation and injectivity analysis have been conducted to estimate the injection rate and pressure, and also to predict the movement of CO2 after injection. A scoping economic analysis of the project was also conducted and presented in the paper.
Quantifying the Effects of Well Type and Hydraulic Fracture Selection on Recovery for Various Reservoir Permeability Using a Numerical Reservoir Simulator
Authors: Shelley R. F. , Lolon E. , Dzubin B. , Vennes M.
Published: February 2011

The industry is faced with the task of producing hydrocarbons from increasingly tighter reservoir rock including ultra low permeability sand and shale. As a consequence, the selection of an appropriate well type and fracture stimulation design is becoming even more critical to project success. The purpose of this paper is to provide some clarity by providing a general understanding about the effects of well type selection and hydraulic fracturing on hydrocarbon recovery for various reservoir permeability scenarios. Well types modeled include vertical, stimulated vertical, horizontal, axial stimulated horizontal and transverse stimulated horizontal with variations in compartment length and effective fracture length. This information has proven useful in the evaluation and planning of moderate to low to ultra low permeability well projects.

The summaries that will be presented in this paper are a compilation of the results from numerous simulator runs for gas, black oil and gas condensate cases. These simulator runs included sensitivities on well type and permeability in order to compare recovery and production. Important conclusions pertaining to the recovery of hydrocarbons from ultra low permeability reservoirs and shale are made. In addition the obvious conclusion about the increasing difficulty of recovering hydrocarbons from lower permeability rock, a primary conclusion is that as reservoir permeability decreases, proper well type selection and effective hydraulic fracture stimulation design become much more crucial. The conclusions also show that for a given permeability, obtaining significant recovery of oil can be a much more difficult problem than with that of dry gas. These conclusions are supported by Bakken and Barnett Shale case histories which are included in this publication.
Numerical Simulation on CO2 Leakage through Fractures along Wells Using Discrete Fracture Modeling
Authors: Huo Da , Gong Bin
Published: February 2011

The first and foremost task for carbon storage is to find proper locations to permanently store CO2 which are injected into deep saline aquifers. However, fractures in the reservoir as well as channels along the wells form preferential pathways for CO2 transport to make it easily escapes from the reservoir. Various scientific studies, pilot CCS programs and commercial CCS projects have shown that leakage problems will be detrimental to the environment and safety to human race.

Modeling CO2 flow in fractures along the well remains a challenge. In this work, several CO2 pathways are characterized, including fractures in cement, casing and the rock. Discrete Fracture Modeling (DFM), which represents fractures individually and explicitly, is applied to simulate CO2 movement in a saline aquifer. This requires unstructured gridding of the saline formation using Delaunay triangulation and transmissibility evaluation between each pair of adjacent cells. Simulations have been done using General Purpose Reservoir Simulator with a non-neighbor connection list.

Several examples including flows through wellbore failures, sloped layers as well as Hydraulic fractures are presented. Through the simulation results, it is found that near well fractures act as extremely preferential flow paths for CO2 transport. Fracturing would help CO2 retained in the target aquifer.

The main application of the framework presented in this paper is to help those involved in evaluation and planning of possible CO2 storage location selection to identify and quantify possible leakage risks through drilling and completion induced fractures.
The Effect of Rheological Properties of Alkali-Surfactant-Polymer System on Residual Oil Recovery Rate After Water Flooding
Authors: Ma Wen-guo , Xia Hui-fen , Yu Hong-yu
Published: February 2011

Through rheological experiments and indoor core experiments, the rheological properties and oil displacement efficiency of Alkali-Surfactant-Polymer (ASP) system containing amphoteric surfactants is studied at ultralow interface tension (0.001mN/m). The effects of changing the concentration of polymer (0.5, 1.0 and 2.0g/L), alkali types (Sodium carbonate and sodium hydroxide) and concentration of Sodium carbonate (0.3-1.5%) on the rheological properties and oil displacement recovery is studied. The viscosity of ASP system increases with mass concentration of polymer increased, and the viscosity of ASP system decreased with mass concentration of Sodium carbonate increased. The viscosity of the system containing 0.6% Sodium hydroxide is higher than the system containing the same concentration of Sodium carbonate. Indoor man-made core displacement experiment results showed: With the mass concentration of polymer changing from 0.5g/L, 1.0g/L and 2.0g/L, the improving value of recovery rate is 25.26%, 21.05% and 22.1% respectively. After water flooding, with the changing of mass concentration of Sodium carbonate on ASP from 0.3%, 0.6%, 1.0% and 1.5%, the recovery rate of ASP systems is 25.26%, 21.42%, 23.81% and 35.35% respectively, the increment of recovery rate is all more than 20.0%, the Total recovery rate is 85.26%, 79.75%, 83.33% and 93.93% respectively. This research results in this paper has important guiding significance on production design.
Integrated Formation Evaluation in an Anisotropic Reservoir Offshore Deep Water Indonesia Using a Combination of Image Logs, WFTs and Mini DSTs for Pay and Hydrocarbon Definition
Authors: Capone Graziano , Malossi Alfio , Mele Maurizio , Damronsak Chantipna , Valdisturlo Antonio , Beretta Enzo , Clementi Alice , Al Shamma Basil
Published: February 2011

Reservoir characterization of laminated turbiditic sequences is often problematic due to the highly anisotropic setting, which affects the formation evaluation from conventional LWD, wireline logs and mudlog data. The reservoir, fluid content and pay petrophysical parameters are usually underestimated. Time and cost constraints can prohibit the utilization of new generation high resolution tools and to perform conventional DSTs.

An oil and gas bearing well in deep water Indonesia was accurately evaluated with a relatively low time and cost investment in formation evaluation and data acquisition. Pay, porosity and water saturation were calculated by integrating high resolution image logs with standard wireline logs. An ample dataset of reliable formation pressures and fluid samples were obtained in a thin bed environment from Wireline Formation Testing (WFT) utilizing standard and large size probes.

Mini DSTs were carried out to characterize reservoir and fluid properties. Thin beds were recognized using an imaging log in oil base mud and through a Thin Layer Analysis (TLA) approach the net sand calculation was enhanced. The TLA result was cross-checked with an electrofacies profile obtained using standard well logs (density, neutron and gamma ray) and calibrated with the sedimentological core description from other wells. In the final net sand computation beds not corresponding with actual reservoir facies were not considered so that only the effective reservoir was included.

The result of this integrated approach resulted in an increase in the net pay evaluation in comparison with the conventional formation evaluation, and confirmed the high potential of nonconventional pay in a deep water environment. An exhaustive reservoir and fluid characterization was also achieved without coring and conventional DSTs.
Superheated Steam Huff and Puff to Revivify a Marginal Pre-salt Heavy Oil Reservoir
Authors: Xianghong Wu , Benjing Dong , Anzhu Xu , Zifei Fan , Ruifeng Wang
Published: February 2011

The Kenkiyak pre-salt oil field is a heavy oil reservoir with the average porosity of 36.6%, the average permeability around 1875x10−3μm2, the buried depth between 290∼380 m, the dead oil viscosity within 144∼691mPa.s @20°C, the reservoir temperatures between 18.8∼20°C. From 1967 to 2002, the reservoir was developed by depletion. As a result, the average reservoir pressure has dropped from 5.9Mpa to 1.8 MPa. The serious heterogeneous characteristics and rapid water invasion made the water-cut of wells as high as 76%. Furthermore, the average well production rate declined from the original 8 m3/d to the later 1∼2m3/d., and was staying at this level for a long time. The field was hovering at the economical margin in 2002. In 2003, the operator launched a series of studies and pilot tests to improve the production performance and economic benefits. But there is no proven current recovery technique that can be economically applicable to such viscous oil reservoirs. However, there are huge amount of hydrocarbon accumulation in such reservoirs that can only be exploited with new concepts. Superheated steam huff and puff as a superior technology for the recovery of high water-cut heavy oil reservoirs has been pilot tested in Pre-salt oil reservoir and has found satisfactory development results. This work introduces this new recovery technique of superheated steam huff and puff to effectively develop serious water-invaded heavy-oil reservoirs, and reviews the main practices we have performed, including simulation studies, pilot tests, challenges encountered and solutions, and current effects. Valuable knowledge and experiences have been obtained in terms of superheated steam huff and puff in such reservoirs after many years depletion development, providing reliable operational experience and technical support for Kenkiyak pre-salt reservoir and similar oilfields.
The Italian Contribution to the European Initiative for the Capture, Transport, and Storage of CO2
Authors: Cau G. , Girardi G. , Macini P. , Mesini E. , Persoglia S.
Published: February 2011

The need to update energy policies worldwide in order to deal with climate change effectively is unanimously considered a priority by the scientific and political communities as well as by the general public. It is also unanimously believed that what is needed is an approach integrating energy usage and production. Such an approach requires that Countries speed up the transition towards an economy not any longer based on fossil fuels, but instead on increased demand/supply efficiency and on renewable sources, while aiming at clean technologies and reducing emissions wherever fossil fuels are used. Italian universities and research centres have started specific studies and programmes regarding CO2 Carbon Capture and Storage (CCS). Such initiatives have been financed thanks to European and National funding. The latter has financed a vast programme based on a strong synergy between national stakeholders, also via the participation to international initiatives like the Carbon Sequestration Leadership Forum (CSLF) and the European Technological Platform for Zero Emission Fossil Fuel Power Plants (ZEP). The main strength of the Italian system lies in the strong will of the Italian Government to adopt a new energy policy. The second strength is the starring of the main Italian industrial subjects, above all ENEL and ENI, which have started important demonstrative projects (not to mention Techint, Carbosulcis, and others). Another important issue is the large quantity of geophysical data available for many parts of the Italian territory that are strategic for assessing the CO2 storage capacity. Finally, Italy is of great interest for the scientific community because of the presence (onshore and offshore) of numerous natural sites of CO2 leaks, thus offering unique opportunities of evaluating its impacts on the natural environment, and of tuning up the monitoring techniques of CO2 leaks.
Case History: First of its Kind: Installation of the Multizone Single Trip MST Technology in Deep Water, India
Authors: Joseph Kevin Peter
Published: February 2011

The paper summarizes the two installations of Multi-Zone Single Trip (MST) technology in deepwater Bay of Bengal, India. The unique challenges of deepwater operations, the technical hurdles, high-stakes economics and the untapped potential rewards have further stimulated the innovativeness of the oil industry stakeholders. In this case, a major private operator in India, a country with growing national energy demands, chose to introduce Multi-Zone Single Trip completion technology in the development of its deepwater gas fields. Historically where sand control is required, cased-hole frac packs have been the preferred completion method, due to its greater completion reliability, relative operational simplicity, higher production rates and greater functionality for multiple zones. However, conventional stacked cased-hole frac-packs require multiple trips, making it both time-intensive and extremely costly in deepwater operations. Multi-Zone Single Trip technology has proven its potential to significantly improve economics by drastically reducing completion time and cost. Despite the significant challenges encountered in these first installations, both wells were successfully delivered with all ten zones treated, five zones per well, with complete sand control and zonal isolation. The paper discusses the challenges encountered, the success factors and recommendations for future projects.
Experimental Investigation on the Viscous Effect on Two-Phase Flow Patterns and Hydraulic Performance of Electrical Submersible Pumps
Authors: Trevisan F. E. , Prado M. G.
Published: February 2011

Using a visualization prototype built from original Electrical Submersible Pumps (ESP) components and with minimal geometrical modifications, a pioneer experimental procedure was developed and conducted to address the viscous effect on liquid-gas two-phase flow through these types of pumps.

Based on dimensionless groups that govern centrifugal pump single-phase performance, two-phase experiments were conducted at different shaft speeds (15, 25, 30 Hz), non-slip void fractions (up to 5%) and viscosity values (46 to 161 cP), while liquid rates were kept constant at 60% of the maximum rate at the defined shaft speed. High speed video footage was taken from the entire impeller flow channel and stage incremental pressure was measured.

The authors identified four liquid-air flow patterns inside the impeller channels: Agglomerated Bubbles, Gas Pocket, Segregated Gas and Intermittent Gas. By comparing the images with the differential pressure data, it was concluded that the Agglomerated Bubble pattern is responsible for the initial head degradation and that the surging event coincides with the Gas Pocket structure, indicating that this is an interface instability problem. Another conclusion made was that the increase in viscosity caused surging to occur at lower void fractions which could be compensated by increasing rotational speed.

The significance of this work is given by the fact that several authors have investigated centrifugal pump performance under two-phase flow; however, previous experiments have been conducted only with water as the liquid, thus neglecting the viscous effect on the two-phase flow mixture. In most of the petroleum industry's applications ESPs operate with oil and natural gas. Thus presenting a knowledge gap between scientific research and field applications, this starts to be addressed in this work.
Evidence of Strong Fracture Height Containment Based on Complex Shear Failure and Formation Anisotropy
Authors: Barree R. D. , Conway M. W. , Gilbert J. V. , Woodroof R. A.
Published: February 2011

For years, uncontrolled fracture heights have been modeled for layered reservoirs using Mode-I tensile failure driven threedimensional (3D) and pseudo-three-dimensional (P3D) fracture geometry models. In these models stress contrast between layers has been assumed to provide the dominant height containment mechanism. Meanwhile, many of the completion diagnostic tools were revealing more contained fracture heights and were thus being discounted. As more diagnostic tools have been employed, it has become apparent that the frac models may have been incorrectly over-predicting fracture heights in many cases. Mine-backs and post-frac coring revealed more contained fracture heights, as did radioactive tracer logs, treating pressure profiles, fall-off data, production modeling, and the absence of perforated interval communication.

This paper will present some of the diagnostic data that support more contained fracture height development. These will include case histories from tight gas sands and shales in which restricted fracture height observations are supported by diagnostic observations. It will also go one-step further, by proposing mechanisms which contribute to fracture height containment. These include poroelasticity, abnormally high "trapped" pore pressure, and complex shear in layered or anisotropic media. It will present some modeling methodologies that place more emphasis on poroelasticity and Mode-II shear failure than current conventional fracture models. The need for investigation, and adoption, of these methodologies will be corroborated by diagnostic data.
Designing and Testing Cement System for SAGD Application
Authors: Patil Rahul , Garnier Andre , Galdiolo Gregory , Patil Sandip , Ravi Kris , Ferreira Luis
Published: February 2011

In recent years, the focus of the oil and gas industry has shifted toward the production of oil from deep and harsh environments. This has been possible because of advanced technologies coming available to the industry. However, challenges still remain in designing materials to withstand certain harsh environment. To satisfy the ever-increasing demand for oil and gas, the industry is tapping heavy oil, which poses unique challenges.

Steam-assisted gravity drainage (SAGD) technique has made it possible to reduce the viscosity of heavy oil and render it mobile. In this technique, steam is injected through an injector well and down to the reservoir where temperature can be raised to 260°C (500°F). This reduces the viscosity of heavy oil but imposes severe thermal stresses on the cement sheath and casing.

Such stresses could hamper zonal isolation and result in the release of steam to the surface. Designing a cement slurry for such applications is challenging of various aspects, such as mixability, pumpability, placement in the annulus, sheath resiliency, permeability, and compressive and tensile strength, that should be optimized to meet the technical, economical, and operational requirements.

This paper details the designing of cement systems for SAGD application and its rigorous testing by simulating downhole conditions. A fit-for-purpose slurry was designed that is chemically stable at the downhole temperatures and able to withstand the thermal stresses.

The optimized slurry was subjected to thermal cyclic loading in an experimental setup designed to simulate downhole conditions, and the performance was evaluated. The cement sheath was intact after being subjected to several thermal loadings. No cracking or de-bonding was observed.

In this paper, the experimental setup, slurry design, testing procedure, and the results are discussed in detail. The discussions presented in the paper should help the industry in constructing and operating SAGD wells safely and economically.
Optimizing Petrophysics Practices through Intelligent Tools Integration
Authors: Al-Harbi Wael , Zahdan Ghassan , Labban Marwan , Rihabe Salim , Husain Kamran , Al-Mushirfi Osama
Published: February 2011

This paper describes several solutions that are developed to automate several workflow processes for petrophysicists at Saudi Aramco. The objective is to further improve the formation evaluation decision-making process by introducing more efficiency in field development practices and automate certain procedures to comply with Saudi Aramco standards. The solutions provided consist of a combination of smart tools and automated workflows designed to further optimize the formation evaluation business processes.

The Near Real Time Petrophysics (NRTP) system enables formation evaluators to simultaneously monitor multiple rigs efficiently by automating the Quicklook workflow. The system seamlessly integrates with well logs and well survey data streams coming from the field with programmable controls that significantly improve the analysts’ ability to prioritize and process well logs on a daily basis.

Workflow Automated Service for Well Logs (WASL) is a collaboration system that optimizes and streamlines reservoir description well log services. WASL enables collaboration among reservoir description data managers, petrophysicists and supervisors. The WASL Dashboard is a complement application to the WASL application suite which monitors and provides key performance index measures on various levels utilizing interactive data visualization tools. The tool also aids Reservoir Description Division (RDD) supervisors by providing engineer productivity statistics, which is currently being used as a measure for granting an appropriate year-end evaluation with respect to well log analysis completion.

The reservoir operation summary environment (ROSE) provides operation engineers with the ability to retrieve all related well log summary activities from the drilling database and allows for the addition of logging plans into corporate repository for daily executive management reporting.
Coil Shooting on Tulip Discovery: Seismic Processing Challenges, Opportunities and Results
Authors: Buia M. , Vercesi R. , Tham M.
Published: February 2011

The Tulip structure is located offshore Kalimantan (Indonesia) in the Bukat PSC. The area is very challenging from the geophysical point of view due the presence of several unfavourable geological factors, especially in the near surface.In order to address these challenges and improve the reservoir image for the appraisal campaign, eni recorded a circular (Coil) seismic survey in August-September 2008. The processing of the survey is now finished. The circular geometry introduces several differences and new challenges in the survey design, acquisition and processing workflow, compared with traditional marine acquisition. When processing a circular survey, the first challenge is the presence of the noise generated by the cables in continuous turning. The second aspect is the presence of statics related to differences in water velocity during the survey. The third difference with conventional processing is related to the midpoint smearing inside the circles, that makes the application of conventional sail line based processing workflows very difficult. The major challenge related to the Coil geometry is an irregular and high fold that requires proper treatment in order to avoid amplitude inconsistencies and migration artifacts. On the up side, Coil geometry allows the full 3D demultiple tools to work at their best and the same is valid for velocity model building and migration algorithms, due to the large azimuthal content. The positive results achieved to date on the pre-stack depth imaging of Tulip, demonstrate that suitable solutions are available even using conventional algorithms and procedures. New processing / imaging strategies need to be put in place in the future in order to minimize the disadvantages and properly exploit the big advantages of Coil acquisition on Tulip.
A Better Way to Forecast Production from Unconventional Gas Wells
Authors: Valkó Peter P. , Lee W. John
Published: February 2011

This work combines two ideas—the stretched exponential decline curve model and the novel paradigm of data-intensive discovery—to provide a controlled production forecast for any individual tight gas/shale gas well on the basis of data gathered through parameter processing for a large group of wells.. Group production for a large number of wells follows stretched exponential decline behavior of production rates, which we model using the corresponding decline curve model. Compared to the Arps model, the new approach offers numerous advantages; the two most significant ones are the bounded nature of estimated ultimate recovery (EUR) without limits on time or rate, and the straight-line behavior of a recovery potential expression that we introduce. This approach moves production forecasts in tight and unconventional gas fields from individual and subjective curve matching to a new methodology we call "group-data controlled forecast." In terms of the novel stretched exponential decline curve model, the combined process offers statistically more consistent reserve estimates and also provides a potential well monitoring tool.
An ESP Lift Reliability Process: Making the Most of Limited Manpower and Field Experience to Promote Field Optimization – Case Study
Authors: Gagner Michael , Wolfe Bryson
Published: February 2011

To optimize production efficiency in a large oil field, engineers must balance their time for troubleshooting production problems among different wells. This is especially true in fields where rod pumps and electrical submersible pumping systems (ESPs) are used for artificial lift.

Typically, engineering time is limited for addressing daily production issues. In many cases where multiple types of artificial lifts are used, 80% of a field's production can come from 20% of the ESP-lift wells: thus the need to keep these higher producing wells operating properly. Unfortunately, downhole ESP operation knowledge is often low compared to rod lift. Consequently, a rod may get proper attention while the ESP may not. The consequences of this can be detrimental in some field environments.

This paper describes key elements of a software ESP management system that boosts an operator's understanding of ESP lift by providing more insight into poor operating conditions than current monitoring systems can provide. Included are potential and present issues encountered during a typical day of operation based on algorithms and automated trending diagnostics. The software management tool can align with existing field management systems to provide the extra knowledge required to keep ESPS operating longer and more efficiently.

The field described in this paper is a CO2/water-flood recovery field. It involves a five-month pilot project where this new ESP management system was established to improve field performance. A detailed description of the process, the issues resolved, and the lessons learned are provided.
Innovative Bearing and Seal Package Improves Rollercone Bit Performance and Reliability
Authors: Day Jeffrey , Yu Jiaqing , Baker Ryan
Published: February 2011

Over the last several years, PDC bits have continued to encroach on traditional rollercone (RC) applications. The expanding PDC envelope has reduced rollercone usage to only the most demanding applications and hard/abrasive formations. Increasingly difficult wellbore requirements dictate that rollercone bits survive more on-bottom drilling/circulating hours with more footage drilled at higher RPM and weight-on-bit (WOB). Additionally, many applications require the use of directional drive systems that apply additional forces on the bit's cutting structure. Additional tool challenges include deep/hot holes, high mud weights, harsh mud chemistry, high temperatures and applications with less than desired solids control.

These hostile down-hole environments contribute to bit damage and can often lead to the failure of moving components, specifically rollercone bit bearings and seals. Failure of any component in the bearing package often results in a catastrophic failure of the entire system, ending the run with the potential of fishing for lost parts. Mud encroachment into the seal is often the reason for bearing failure.

To solve this problem, extensive analysis of field data and dulls was conducted to identify the conditions limiting seal/bearing life. The solution was identified and new bits were developed during field tests. Field testing included a large data set of 28 test runs against 61 control runs, all in the IADC 527-537 range and in the same application. The test results show and improvement in seal life of the test group of 26.9% over the offset data set. Since these results, testing has expanded to four different bit sizes and bit types. This paper will outline the significant time/cost savings to the operator in the test area.
Deconvolution of Pressure and Rate Data from Gas Reservoirs with Significant Pressure Depletion
Authors: Levitan M. M. , Wilson M. R.
Published: February 2011

Deconvolution is a technique for converting the pressure and rate data obtained from a well operating under variable rate conditions into a much simpler form of constant-rate drawdown pressure response function from the same well. However, deconvolution should only be applied to pressure and rate data that result from fluid-flow in the reservoir that is governed by a linear set of equations. In gas reservoirs, the fluid flow problem is non-linear because the gas properties are strongly dependent on pressure. In some specific situations, this gas-flow problem can be linearized by the use of a pseudo-pressure transform which allows deconvolution to be successfully applied to that data. However, there are situations when a pseudo-pressure transform alone does not fully linearize the gas-flow problem and the resulting data will exhibit non-linear behavior caused by the pressure dependence of the gas compressibility. Direct application of deconvolution to such data will produce erroneous results.

This paper presents an enhancement of the deconvolution algorithm that allows it to be used with pressure data affected by a non-linear pressure-dependent compressibility. We discuss the detailed considerations for this enhancement of the deconvolution algorithm and demonstrate its performance on simulated test data exhibiting this non-linear behavior. We also demonstrate the application of this enhanced deconvolution algorithm to a set of pressure data from a gas well fitted with a permanent gauge and covering the first three years of production from that well.
A Comprehensive Model of High-Rate Matrix Acid Stimulation for Long Horizontal Wells in Carbonate Reservoirs
Authors: Furui K. , Burton R. C. , Burkhead D. W. , Abdelmalek N. A. , Hill A. D. , Zhu D. , Nozaki M.
Published: February 2011

Matrix acidizing models have traditionally under-predicted acid stimulation benefits due to under-prediction of wormhole penetration and corresponding completion skin factors in vertical wells. For long horizontal wells drilled in carbonate reservoirs, productivity enhancement is a function of acid placement and effective wormhole penetration. However, prediction of wormhole penetration requires more effective analysis than provided by current industry models. This paper presents results of matrix acid modeling work for horizontal wells and describes a practical engineering tool for analyzing the progress of matrix acid stimulation for cemented and un-cemented horizontal well completions typically employed in carbonate reservoirs.

An integrated flow model has been developed to predict the wellbore pressure profile and wormhole distribution by tracking the movement of the acid in the wellbore and the formation. Analysis of injection rates and pressures during acid treatment provides engineers with a way to determine the varying injectivity and tubing friction as stimulation proceeds. The model presented here can be used as a forward model for analyzing real-time treatment rate and pressure histories and can also be used to review past treatments to improve future treatment designs.

The wormhole growth model is based on Buijse and Glasbergen’s empirical correlation augmented by the effect of formation heterogeneity and scale-up procedures that extend the wormhole geometry and penetration from laboratory flow tests on small cores to field-size treatments.

Application of this modeling shows acid wormholing through carbonate formations can provide significant stimulation resulting in post-stimulation skins as low as −3.5 to −4.0 vs. previously predicted values in the −1.0 to −2.0 range. Using actual field stimulation data, we also discuss key elements to successful stimulation planning and the diagnosis of matrix acid treatments to achieve effective wormhole coverage for horizontal completions in carbonate formations.
Enviromental Management Performance of Subang Field, PT Pertamina EP, Indonesia on Proper Indicator
Authors: Sembiring Indra P. , Mulyono Eka Adhi
Published: February 2011

Introduction

Oil and gas exploration and production activities are faced with major challenge these days, when they deal with HSE issues especially for environmental issues. This paper describe environmental management performance at Subang Field, PT. Pertamina EP, Indonesia based on PROPER indicators as parameters to comply government regulation

Existing Condition

PT Pertamina EP is a state-owned oil and gas company, engaged in managing the upstream oil and gas production through a more manageable exploration and exploitation activities, consists of 18 field that operated all over Indonesia.

Based on Government's Law of Environmental Management, PT Pertamina EP has to manage all of upstream activities, including environmental aspects, especially environmental impact caused by upstream activities.

Government already set up parameters to evaluate company performance of environmental management. The instrument for that purpose is PROPER.

PROPER is an integrated strategy of Ministry of Environment to implement Law number 23 Year 1997 regarding Environmental Management. There are four main activities in its implementation include monitoring of company's compliance, applying transparency in environmental management or public right to know, involving public participation in environmental management and obligation of company in submitting environmental management information.

PROPER consists of 5 (five) categories: Gold, Green, Blue, Red and Black.

Subang Field, is one of field that operated by PT Pertamina EP, located at West Java. The average of oil production from this field is 15.000 bopd. At 2009 Subang Field achievement for PROPER is Green. It has applied successfully not only government's environment regulation but also good relationship to community around Subang Field.

To achieve PROPER Green category, Field Subang has utilized and managed environmental parameters such as: Waste managemet system (water, emission, and hazardous and toxic material)Implement ISO 14001Energy conservationCommunity development.

The result shows that Subang Field had committed to implement environmentally friendly for all of activities which green process give some advantages for nature resources and community.
Joint Inversion of Temperature and Pressure Measurements for Estimation of Permeability and Porosity Fields
Authors: Duru Obinna O. , Horne Roland N.
Published: February 2011

The acquisition of temperature measurements from wells using downhole devices such as Distributed Temperature Sensors (DTS) and Permanent Downhole Gauges (PDG) is becoming a common practice in the industry. Temperature data acquired continuously at the perforation sandface show transients that may contain information about the characteristics of the producing formation, presenting an opportunity for the combination of flow and heat transport models in reservoir characterization. The physical model for temperature distribution in a reservoir during production shows a strong dependence of temperature on the porosity distribution. The dependence of this model on permeability is weakly linked to flow through convection. On the other hand, the model for flow is more strongly dependent on permeability than on porosity. These models are coupled through the dependence of the heat model on flow velocity, and the dependence of the flow model parameters on temperature.

In this work, the heat and flow models were inverted jointly to obtain an estimate of the permeability and porosity fields in a synthetic reservoir, using combined quasilinear Bayesian inversion methods and Ensemble Kalman Filter (EnKF) for data assimilation. A first posterior mean and covariance of the log-permeability and porosity fields were found using the first set of data and the quasilinear inversion approach (similar to the maximum a-posteriori probability MAP estimate). The ensembles in EnKF were then obtained as conditional realizations using these statistics. The production data (bottomhole pressure and production rates) and temperature measurements were then jointly assimilated with each advancement in time, to obtain log-permeability fields that compared favorably with the true permeability fields, and porosity fields that also compared favorably with the true porosity field.

Also, it was found that the inclusion of temperature measurements improved the resolution of the estimates of both porosity and log-permeability in the test cases, compared to using only production data. Particularly, the porosity fields showed marked improvement with the addition of temperature measurements. The results demonstrate that temperature measurements that are now routinely obtained in producing fields are a potential source of relevant data for constraining characterization of heterogeneous reservoirs.
Numerical Simulation on Three Layer Dynamic Cutting Transport Model and Its Application on Extended Well Drilling
Authors: Wang Zhiming , Zhai Yujia , Hao Xining , Guo Xiaolei , Sun Lili
Published: February 2011

Hole cleaning is one of the key issues in extended reach drilling, the thickness of cutting bed monitor and control is the critical technique which urgent to solve. Based on solid-liquid flow mechanics, considering actions between the layers, slip between solid and liquid phase, and rotation of drill pipe, a three layer dynamic cutting transport model was developed, staggered mesh and Stability Enhancing Two Step method were adopted for the simulation. The influence factors of the thickness of cutting bed were analyzed, ECD with variable cutting bed can be accurately predicted, by compare the measured ECD with the theoretical value, the thickness of cutting bed can be monitored, and this technique has been successfully used in the oil field of South China Sea.

The research results show that high angle hold segment is the most difficult segment for cutting transport. The pump can not reach the minimum flow rate for keeping the hole cleaning. Low viscosity drilling fluid, high flow rate and drill pipe rotation should be adopted, and when the thickness of cutting bed exceeds 10%, flushing method must be used to remove the cuttings, the recommended flushing period is 150m. By this model, the dynamic process of cutting transport during drilling and flushing can be simulated. Giving a guideline to the design of hydraulic parameters, and offering an effective field method to monitor and control the hole cleaning in extended reach well.