bluuebunny/crossref_metadata_2025 huggingface dataset:
Interpretation of Multirate Tests by the Pressure Derivative - I. Oil Reservoirs
Authors: Tiab D. , Ispas I. N. , Mongi A. , Berkat A.
Published: December 2007

Pressure build-up data in low permeability reservoirs take too long and are usually of poor quality. It is often not economically feasible to shut in a well with a high production rate for a buildup test. Sand producing wells are not good candidates for long pressure drawdown tests. It is often impracticable to maintain a constant rate long enough to complete a drawdown test. In these cases, a multi-rate flow test should be run instead of buildup or drawdown tests. Actually a well-designed multi-rate flow test may minimize the influence of wellbore storage on pressure data.

A new technique based on the pressure derivative concept is presented for interpreting a multi-rate flow test. It is shown here that a Cartesian plot of the pressure derivative data versus a time group is a straight line from which the reservoir permeability can be estimated. It is also shown that for the case of two-rate test, Tiab's Direct Synthesis technique is applicable for calculating permeability and skin

A step by step procedure is presented for interpreting a multirate test using pressure and pressure derivative data. This new technique is illustrated by several numerical examples.
Buildup Solution in a System with Multiple Wells Producing at Constant Wellbore Pressure.
Authors: Camacho-V. Rodolfo , Galindo-N. Agustín , Prats Michael
Published: December 2007

This paper presents a new analytical solution to obtain the shut-in wellbore pressure in a two-dimensional closed-boundary reservoir with multiple wells producing at constant different wellbore pressures.

The analytical solution is obtained in the Laplace space, by using separation of variables, Green's functions, and the unit step function, similarly to the method proposed by Rodriguez and Cinco-Ley1 and Camacho-V. et. al.2 However, instead of using a large time approximation for Green's functions, we used a Taylor series expansion, which makes the inversion problem very simple, avoiding the use of a numerical inversion algorithm like that proposed by Stehfest, at early shut-in times.

This solution allow us to study the interference of producing wells during the build-up test.
Drilling in South America: A Wellbore Stability Approach for Complex Geologic Conditions
Authors: Willson S. M. , Last N. C. , Zoback M. D. , Moos D.
Published: December 2007

An analysis approach is described which includes the effects of rock fabric strength anisotropy on wellbore instability. When drilling in geologically complex conditions - shown to be commonplace in the Andean foothills of South America - bedding-plane slippage, resulting from an unfavourable interaction between in-situ stresses, the well trajectory and bedding, is shown to cause severe instability for certain well trajectories. Case-history examples from the Pedernales field (Venezuela) and Cusiana field (Colombia) are presented which confirm the analytical predictions.
Hydraulic Units in Traditional Areas of Eastern Venezuela
Authors: Rampazzo M. , González G. , Ferrer A. , Iraldi A. , Alvarez R.
Published: December 2007

The highly lenticular character of the reservoir sands present in the traditional fields of Eastern Venezuela Basin, led to the establishment of multiple reservoirs, which were completed individually for exploitation. This production scheme and the current low well production rates, result in a low profitability to maintain these reservoirs active. For increasing productivity, here it is proposed to complete more than one sand simultaneously.

In order to determine the possibility of sand layer communication, the information of six different traditional fields was reviewed, as a result, the Acema Casma area was proposed as the best area for a pilot project. This project will be used to monitor the results of a different completion outline, thus allowing the establishment of a general plan, to cover other fields in the traditional Eastern Basin.

According to the well simulation analysis the combined production of more than one sand, allows to produce the reserves in a shorter time, increasing in a significant way, the Net Present Value, and diminishing the risk of well mechanic damage. One of the big limitations of this study was the lack of enough reservoir information, for that reason the pilot project includes to take additional data like well pressure.

Where sand layers are not in communication, commingle production should be surely evaluated in the future, whenever, the compatibility of the crudes and the effective production monitoring is guaranteed. In order to make the appropriate decision regarding these traditional field exploitation, a detail reservoir characterization, that includes additional data is absolutely necessary.
Enhanced Drill Cuttings Analysis for Drill-in Fluids Design
Authors: Guzman Jose H.
Published: December 2007

Even though drill cuttings are first hand actual reservoir information, their conventional analysis during mud logging is limited and under estimated as source of relevant information. Drill-in fluid design becomes successful if bridging materials such as sized salt or calcium carbonate is matched with pore geometric attributes of formation rock.

A novell approach for drill cuttings analysis is being under use to select the optimum sizing for bridging material, when there is no core information available.

After using a combined technique of Scanning Electron Microscopy (SEM), chemical analysis by Energy Dispersive X ray Spectroscopy (EDS) and Backscattered Electron Images (BSEI) digital processing and analysis, it is possible to get key parameters to design a more efficient Drill-in fluid. It can help also in the selection of screens for solids control in surface equipment.

Textural parameters found with this technique include grain size distribution, shape and sorting. Porous space description such as (2D) porosity and pore throat size distribution, that can be obtained in grain clusters coming from drilling consolidated rock horizons. Rock fracturing trends, natural or induced can also be observed. Therefore a more detailed sample description is achieved in relation to conventional analysis.

Once this information has been processed, laboratory filtration tests can be performed on available reservoir or similar synthetic material, in order to recommend a better formulation of Drill-in fluid for field use.
Intermittent Gas Lift Optimization in Rosa Mediano Field
Authors: Hernandez A. , Perez C. , Lobo W.
Published: December 2007

Rosa Mediano is the field with the lowest reservoir pressure in Lake Maracaibo. For this reason, a large number of wells are currently producing on choke controlled intermittent gas lift. The objective of this work was to identify operating conditions that could be modified in order to optimize gas consumption and maximize liquid production.

To carry out this objective, more than 50 down-hole pressure and temperature surveys were run in a total of 7 oil reservoirs. The survey procedure was such that an important number of engineering parameters could be obtained: real liquid pressure gradient, optimum cycle time, liquid fallback and the productivity index of the well.

Important deviations of the dynamic behavior of spring loaded and nitrogen charged gas lift pilot valves were identified and they are presented in this work. The analysis of down-hole pressure surveys also shows that, in many cases, the liquid fallback was well above the usually assumed 5% of the initial liquid column length per thousand feet traveled. These measurements are presented in the paper, together with a discussion of possible causes.

The proper gas injection pressures, gas volume injected per cycle and optimum cycle times were calculated from the reservoir inflow capabilities. An overall 30% increase in liquid production was obtained when these parameters were adjusted to new values calculated from the survey analysis. A shift from choke control to the use of surface controllers was necessary in some cases and detailed examples are presented in the paper.

Finally, the analysis of down-hole pressure surveys performed on 6 double packer Gas Lift Chambers shows that this type of completion is highly inefficient for wells with moderate to high formation gas-liquid ratios.
Killing Methods and Consequences of 1120 Gulf Coast Blowouts During 1960-1996
Authors: Skalle P. , Jinjun H. , Podio A. L.
Published: December 2007

This paper focuses on what happened after wells are out of control by analyzing statistically a database that contains about 1120 blowout events from the Gulf Coast and adjoining states covering the period 1960-1996. The trends are extracted, including blowing fluid type, mode of control, duration of blowout, pollution, fire and explosion, and fatalities. Detailed differences between Outer Continental shelf (OCS) and Texas are given. A report form of blowout events is recommended in order to improve the data quality and standardize reporting.
Impact of Heterogeneities in Horizontal Well Performance
Authors: Portella R. C. M. , Lanzarini W. L.
Published: December 2007

In order to be viable economically, horizontal wells must present a high productivity. Reservoir heterogeneities can affect greatly this productivity; thus, a good evaluation of the well productivity in heterogeneous reservoirs is essential to guarantee the economical success of oil field development projects. Although tools based on analytical or semi-analytical techniques are useful for a preliminary evaluation of the performance of a horizontal well, their limitations (homogeneous reservoir, no gravity, and single-phase flow) can affect greatly the results. Hence, only the use of a full simulator model can provide an accurate response of the productivity of a horizontal well in a heterogeneous reservoir.

In this paper, we analyze the impact of the heterogeneities in the productivity of horizontal wells in channeled turbidite reservoirs, which are the most common reservoirs in offshore oil fields of Brazil. We use a conventional simulator to do the analysis, and a graphical front-end was developed to simplify the task of setting up simulation data sets. A Boolean stochastic technique was used to model these kinds of reservoir. Several conditional images were generated using this stochastic method. Flow simulations were performed in each of the images and the results were compared. The better characterization of the reservoir combined with a full simulator model provides a much better analysis of the risks involved in the development of a field with horizontal wells.
Asphaltene Stability in Crude Oils
Authors: Rogel E. , León O. , Espidel J. , González J.
Published: December 2007

The influence of different factors on the asphaltene stability in crude oils was evaluated. Compositional studies and structural characterization of resins and asphaltenes were carried out in order to study a possible relationship between these properties and the asphaltene deposition behavior. Asphaltenes were obtained by precipitation with n-heptane and characterized by elemental analysis and spectroscopic techniques. Low hydrogen to carbon ratios, high aromaticities and high condensation of aromatic rings were the main characteristics of the asphaltenes from unstable crude oils. According to these results, the stability behavior of the asphaltenes was strongly influenced by their structural characteristics. However, it was also found that stabilization by means of a commercial inhibitor was affected by the composition of the crude oil. In particular, a high content of basic functionalities in the crude oil can be related to the decrease of the inhibitor's effectiveness (dodecylbenzene sulphonic acid). Based on these findings, some useful suggestions applicable to the oilfield operations are made.
Pseudo Relative Permeability Functions. Limitations in the Use of the Frontal Advance Theory for 2-Dimensional Systems
Authors: Telleria M. S. , Virues C. J. J. , Crotti M. A.
Published: December 2007

To obtain a reliable characterization of complex reservoirs, they must be represented with fine scale models. However, detailed descriptions demand a huge amount of information and processing time. Therefore, less complex models are usually designed. To construct these simplified models, pseudo relative permeability curves are developed. Pseudos reduce the number of dimensions of reservoir models, trying to reproduce the behavior of the fine scale system. Simplifying 2-dimensional (2D) systems to 1-dimensional (1D) models allows reservoir engineers to apply them to simple calculations and less complex reservoir simulations. Once reduced to 1D, models are usually analyzed by means of frontal advance theory.

In this paper, stratified systems under no cross-flow and under vertical equilibrium (VE) conditions were studied by means of numerical simulation (NS), analytical methods and simplified pseudo relative permeability functions (PRPF). When frontal advance theory was used, some restrictions were found to the application of pseudo functions. These limitations, if overlooked, could yield wrong conclusions.
Volatile Oil. Determination of Reservoir Fluid Composition from a Non-Representative Fluid Sample
Authors: Cobenas Rafael H. , Crotti Marcelo A.
Published: December 2007

Volatile Oil reservoir are sometimes evaluated as gas and condensate systems when pressure in the well neighborhood reaches values fairly below saturation pressure. This pressure drop is common in almost all reservoirs at late depletion stages or from the beginning in tight formations. When this situation occurs, it does not matter how carefully the sample is taken, it always leads to non-representative PVT analysis. Based on a real case study on a tight formation, sampled at the beginning of production history, a dynamic data integration between petrophysical and thermodynamic information was conducted in order to understand overall reservoir behavior. As part of this integration, a compositional material balance was developed in order to describe the reservoir performance against pressure. A sensitivity case to relative permeability curves was run with the material balance. The fairly good matching of the material balance model with the production test allowed us to determine the most probable reservoir fluid composition. It was also noted that the relationship between GOR and separator fluid composition had negligible dependence on relative permeabilities.
Development and Validation of Interference Testing Analysis Model Using Boundary Element Method for Geometrically Complex Reservoirs
Authors: Sung W. , Lee W. , Kim I.
Published: December 2007

The primary focus of this paper is on the development of a well testing model to analyze the data from geometrically complex reservoirs. The model employs a boundary element method applying the weighting function of the free-space Green’s function which is applicable to multi-well system. Because of the characteristics of the methodology implemented in this study, the developed model is capable of handling the data acquired from multiple sources or sinks in an arbitrarily shaped system. This technique is free from the grid orientation effect and numerical dispersion as well. The proposed model has been verified and validated for simple geometrical systems (square and circular) whose solutions can be obtained by the image well technique, and their matches are found to be excellent. Finally, the applicability of the model has been checked by using the synthetic multiple well testing data in a geometrically complex bounded reservoir. In this test, from the anisotropic analysis, it was found that the anisotropicity (kmax, kmin, and direction of major flow) was determined.
Yakin Field: Innovation Breathes a Second Life to the Mature Oil Field
Authors: Kuntjoro M. B. , Palar S. , Bouclin D.
Published: December 2007

Yakin field, operated by Unocal Indonesia Co. was discovered in May 1976. The field was divided into three separate fault blocks and located offshore Balikpapan in 15-ft water depth. By the end of year 1996, the field had produced 33.9 MMBO and 25.2 BCF gas. The field’s daily production had declined to 2,900 BOPD and 4.4 MMSCFD gas from 19 producing old wells scattered on small platforms.

Prior to 1997, a transition zone 3D seismic was acquired over the whole area identifying potential for additional reserve recovery. Development drilling had not been done for eleven years due to high drilling cost to develop marginal reserves. The field is located in shallow water depth with platform size limiting drilling operations to a jack-up and workovers to a snubbing unit. However, with the innovation of a new wellhead platform structure, a less expensive tender supported rig could be used. Cost reductions in development drilling, made marginal reserves economic.

Field performance review, geological and 3D seismic work, pilot wells and reservoir simulation indicated reservoir development potential in the field through the application of horizontal drilling technology. In 1997 an additional fourteen wells were drilled and completed in Yakin field. With the addition of these new wells, the total field production increased to 7,200 BOPD. The cheaply drilled horizontal wells, were found suitable for controlling sand production in the unconsolidated Yakin reservoirs.
Marginal Field Development Strategy, Kartini Field, Offshore Southeast Sumatra
Authors: Thomas Budiyento , Galuccio Miguel M. , Dharma Wira , Mitrodihardjo Sudharmono , Pasaribu Jonny
Published: December 2007

Kartini field was discovered in 1977 and was followed by the drilling of three delineation wells. The reservoirs are fluvial sandstones of the Gita member, Talang Akar Formation that contain gas, oil and water. Kartini-1 and −2 tested at 4,485 BOPD and 2,944 BOPD, respectively. Trapping is created by combination structure and stratigraphic pinch out along the channel edges. In 1992 the initial plans were to develop the field by installing a 9-slot platform and drilling 8 development wells. The well locations were based on 2-D seismic and un-migrated 3-D seismic data. The first two wells were drilled in the field and resulted in uncommercial wells. Maxus ascertained that the development risk was high and put the field's development on hold.

Subsequently the seismic data was migrated which allowed Maxus to utilize the seismic attributes in conjunction with a new geological interpretation to remap the main productive reservoirs.

During this hiatus period, Maxus's experience with caissons progressed from a simple design with a maximum three wells without workover capability to the current technology allowing up to eight wells with workover capability. This improved technology results in significant cost savings and allowed the Kartini field to be developed economically. In addition to the deviated wellbores, three horizontal wells will be drilled and are designed to drain reserves from thin oil-bearing sandstones that would be uneconomic otherwise.

Based on new seismic and geological interpretations, installation of a low cost Guardian structure, and utilization of horizontal wells, Kartini field was developed as an economic field with production beginning in October 1998.
Reservoir Impairment Mitigation: Successful Use of Graded Carbonate Drilling Fluids
Authors: van Vliet J. P. M. , Hjh Rosita Hj Hassan
Published: December 2007

With the ongoing technological developments in horizontal drilling, multilateral wells and open hole completions, it has become very important to drill and complete the reservoir sections of a well inducing as little impairment as possible. Drilling, clean-up and completion practices should be tailored to minimise formation damage, thereby maximising the productivity of the well. Since mid ‘97, Brunei Shell Petroleum has drilled a number of horizontal well sections that were completed with a sandscreen only or with a horizontal gravelpack. The success of these operations is illustrated by the fact that the reservoir sections showed expected or better than expected productivity, even when in one case the reservoir was severely depleted.

Based on research work done before the drilling campaign started, the reservoir drilling fluid selected for these wells was a graded carbonate drilling fluid. This paper gives details on the selection process, and it describes the successful use of the drilling fluid in the field. It also details the procedures followed during drilling and completion of the wells, which successfully minimised impairment of the reservoir sections.
Overcoming the Challenges of Shallow Horizontal Drilling in the World's Largest Steamflood
Authors: French Michael R. , Siagian Mangojak , Thurston F. Kent
Published: December 2007

This paper is a case history that documents the drilling and completion program of a horizontal steamflood project in a very shallow sandstone reservoir. A total of nine (9) medium radius horizontal wells were drilled at a depth of + 600’ TVD using a vertical mast rig. The factors that influenced the decision to use a vertical mast rig instead of a slant rig are reviewed. This decision presented additional challenges to the drilling personnel, production engineers and the subsurface engineers. Steps taken to address these challenges are discussed as well as the development of special drill collars that played a key role in the success of this program.
Implementation of a Company-Wide Production Monitoring System
Authors: Hidayat Noor , Gadjah Mada Asli , Muchsan Asfaril , Ismayadi Budhi
Published: December 2007

PT Caltex Pacific Indonesia (CPI) is the largest crude oil producer in Indonesia under Production Sharing Contract (PSC) with PERTAMINA. Its field operation is located in Riau province, Central Sumatra.

Field and well performance monitoring for company-wide daily production monitoring systems in CPI is one of the very critical aspects to supporting company’s vision, mission, and performance measures. It even becomes more important after the commencement of the Strategic Business Unit (SBU) organization. Therefore, CPI needs to have an integrated and flexible systems operating on daily basis. We name the system DREAMS-NT (Data Resources for Engineering Analysis and Monitoring Support - New Technology), and it has been put on operation since January 1st, 1998.

This paper will discuss in brief all the phases involved in the project, with a guideline from CPI’s Asset Management Process, which includes Systems Requirement Definition, Alternative Solutions Assessment and Selected Solution Recommendation, Systems Implementation Plan Layout and Execution, and Post-Implementation Plan of DREAMS-NT.

The more focus aspect that will be discussed in this paper is the technology aspect for implementing the system: the IT infrastructure requirement, the server platform, the client PC requirement and configuration, the relational database platform, the distributed database configuration, the interface in the database level to other systems, and the interface to CPI intranet web server. In the application itself, there is a specific feature called GRANI (GRAphical Network Interface) that provide the easy of use and flexibility to draw the crude oil flow from well to gathering station, to shipment meter, to shipping tank, and to selling point. In other words, this GRANI represent the actual crude oil piping network from wells to the selling points. A mathematical formula can be embedded in this GRANI drawing of piping. At the end, we also discuss benefits gained with the implementation of this system with its ‘new’ technology.
Rod Pumping Technique Without Tubing
Authors: Xu Xiufen , zheng JiangMin , Jun Zhu
Published: December 2007

To minimize the initial investment of pumping wells, a rod pumping technique without tubing(hereafter referred to as tubingless rod pumping technique) is studied in this paper. Its principle is: a packer is lowered to the designed setting depth and set down, an inserted pump assembly is inserted into the inner bore of the packer, a seal and a fixation are formed between the pump barrel outer surface and the packer inner bore, the annular space between casing and rod string is the oil flow passage. The rod string is hollow, at its bottom, a downward check valve is screwed. When the oil well produces, the check valve is closed. When well cleanup is required, wellflushing fluid is pumped from ground to the bottom hole through the hollow rod string and check valve, and wellflushing fluid returns to ground through the annulus.

Compared with the conventional rod pumping system with tubing, one pumping well without tubing decreases its investment of tubing string by approximately 40-50 thousand yuan. This paper analyzes the reliability and economy of this technique. The field test results of three wells in the Daqing Oil Field are given in this paper, two of the wells have been producing normally for about one and a half years.
Pressure Transient Technique Adds Value to ESP Monitoring
Authors: Spath Jeff , Martinez Alex D.
Published: December 2007

A novel pressure transient technique is combined with routine performance monitoring of ESP's to economically characterize the well/reservoir producing system.

Information derived from the proposed procedure enables the engineer to compute the maximum production of the well and to decide what productivity improvements may be employed to achieve this maximum. Specifically, accurate values of permeability, damage and average pressure may be obtained as well as the presence of heterogeneities and their characteristics. In a multi-well implementation, the procedure allows both the temporal and spatial variation of reservoir properties and fluids to be monitored.

Fundamental to the technique is the modulation of the well's flow rate to produce an unambiguous pressure response. Flow rates are modified programmatically using variable frequency devices which vary the speed of the ESP; we consider several possible flow rate scenarios and discuss the practical implications of each. The resulting pressure response is modeled analytically, continuously and automatically, in a least squares sense, to monitor the well and reservoir properties. Computational considerations are discussed.

The objective of this paper is to allow operators to optimize production rates and recovery while minimizing capital investments and operating expenses. The efficacy of the technique described is demonstrated using simulated data.
The Role of Geology in Stochastic Reservoir Modelling: The Future Trends
Authors: Tamhane D. , Wang L. , Wong P. M.
Published: December 2007

Stochastic simulation is a popular approach for the quantification of reservoir heterogeneity. From the geological viewpoints, however, the role of reservoir geology in stochastic models is diminishing in recent years. This paper reviews the major characteristics of the stochastic models, and geological knowledge is identified as the major missing element in the current practices of the simulation techniques. A detailed discussion of the meaning and usefulness of geological knowledge is given. We have also provided a list of future research directions showing how we can make use of conceptual geological models to bridge the gap between reservoir geology and stochastic simulation practices.
Reservoir Simulation for a Low Productive and Strongly Heterogeneous Carbonate Reservoir in the Arabian Gulf by Geostatistical Approach
Authors: Wannabe Kazuaki , Suzuki Satomi , Eto Koji , Samizo Nobuyuki
Published: December 2007

The reservoir simulation model for a low productive and strongly heterogeneous carbonate reservoir was constructed by upscaling the detailed geological model. First, geological model was constructed and the three dimensional distribution of petrophysical properties were generated by geostatistical approach. The absolute permeability and relative permeability endpoints were excellently correlated to the core data by the application of electrical facies (EF) grouping which was newly developed (Refs. 1 and 2). The successful history match was obtained by incorporating the high permeability streaks into the model to simulate the abnormal reservoir pressure trend. This high permeability streak was distributed by sequential indicator simulation (sIs) based on the combination of two types of possible log attributes.
Optimum Spacing of Multiple Stabilizers to Increase Critical Buckling Load of BHA in Slim Hole Drilling
Authors: Akgun Ferda
Published: December 2007

Cost effective drilling rate necessitates the adequate application of weight on the bit. Weight on bit is provided by means of Drill Collars (DC). As DC diameter gets smaller with the reduced borehole diameters as in the case of most slimhole drillings, their resistance against buckling, known as Critical Buckling Load (CBL), decreases. This may cause major drilling problems such as; undesired hole deviations, pipe failures and slow drilling rates.

Weight supporting capacity of DCs can be improved by the placement of stabilizers in bottom hole assembly (BHA). However stabilizer position in the BHA is one of the major factors, which effects the CBL of DCs.

In the first part of this paper a finite element method will be presented to assess the CBL of DCs. Then, CBLs of DCs with stabilizers placed at different configurations will be presented in the second part of the paper.
Oil Recovery Mechanisms of Alkali-Surfactant-Polymer Flooding
Authors: Arihara N. , Yoneyama T. , Akita Y. , XiangGuo Lu
Published: December 2007

The experimental study includes phase behavior tests, measurements of interfacial tension (IFT), and coreflood tests. Effects of alkali (sodium carbonate) additives on micro-emulsion phase behavior were determined for a reservoir oil. No emulsion phase was generated for low surfactant concentrations without alkali additives, while an emulsion phase was always formed with alkali. Measurements of the dynamic IFT revealed that when the alkali concentration is as high as 0.7–1.0 wt%, the IFT rapidly increases after about 100 minutes, which suggests that the system shifts from the middle to upper-phase equilibrium.

Based on tertiary alkali-surfactant-polymer (ASP) coreflood tests with surfactant and polymer concentrations of 1.0 wt% and 1200 ppm respectively, an optimum alkali concentration was confirmed as 0.2 wt% that allowed the highest recovery. Using the optimum ASP concentrations, another series of corefloods were conducted to evaluate the effect of remaining oil saturation at the start of ASP flood. Mobile oil helps alkali and surfactant slugs form an oil bank. In order to examine the oil recovery by high alkali and low surfactant concentrations (1.3 and 0.1 wt%, respectively), corefloods were conducted by changing the injection volume and scheme. Only a small incremental recovery is obtained with ASP slugs higher than 0.2 PV each. The injection scheme of polymer slugs is confirmed to be crucial for ASP flooding. Parallel coreflood tests as physical simulation of ASP flood in a two-layer system showed recovery performances complicated not only by permeability contrast but also by small-scale heterogeneity within inidividual cores.

Acceptable matches between coreflood experiments and one-dimensional flow simulation were obtained by modeling ASP flood with recovery mechanisms of the surfactant-polymer flooding.
Microbial EOR Laboratory Studies and Application Results in Daqing Oilfield
Authors: Zhang Yijiang , Xu Zhengshun , Ji Ping , Hou Weihong , Dietrich Forrest
Published: December 2007

Microbe inoculation of Daqing crude samples in the laboratory reduced oil viscosity, indicating microbe effectiveness. Field application of the same strains of microbes resulted in a thousand-fold increase in both concentration and total number of microbes in the water produced from the reservoir. The data proves existence of active, thriving microbe colonies in the reservoir in a manner not previously reported, compatibility between the microbes and Daqing oil in the reservoir, and propagation in the reservoir. The microbe detection method is reviewed along with microbe growing details in four wells. Overall field results in twenty-five wells are described, proving microbial EOR (MEOR) is suitable for use in Daqing Oilfield.
Well Abandonment—A "Best Practices" Approach Can Reduce Environmental Risk
Authors: Kelm Charles H. , Faul Ronnie R.
Published: December 2007

Wells are drilled and completed for a typical production life of 15 to 20 years. After a well is depleted, it must be abandoned so that the permeable intervals penetrated by the wellbore are isolated. For an abandonment to be successful, it must stabilize the wellbore and its associated annuli until geologic forces can re-establish the natural barriers that existed before the well was drilled. The isolation of the hydrocarbon-bearing intervals, overpressured intervals, uncemented annuli, and any freshwater intervals penetrated by the wellbore is critical to successful abandonment. The abandonment plan must be based on the types of fluids contained in reservoirs and the well's mechanical condition at the time of abandonment. Government regulations for well abandonment are minimal guidelines for abandonment, and should not be considered finite answers to environmental safety issues.

This paper describes "best practices," concepts and techniques that operators should consider during abandonment planning, that will help ensure effective isolation within the wellbore.
Exploration and Production Operations - Waste Management a Comparative Overview: US and Indonesia Cases
Authors: Bansal K. M. , Sugiarto _
Published: December 2007

Waste management programs in Exploration and Production Operations (E&P) are discussed in this report. Regulatory guidelines in Indonesia are briefly described and compared with the guidelines in the U.S. Waste treatment and disposal practices commonly used in the U.S. are also discussed. Pertinent regulatory guidelines for the use of some of these technologies in the U.S. are presented. This information was gathered to identify potential applications, based on the experiences in the U.S., for developing cost effective and environmentally sound E&P waste management strategies in Indonesia.

Wastes from E&P operations fall into four general categories: (a) produced water from production operations, (b) drilling, completion, and workover wastes, (c) associated wastes, and (d) industrial wastes. The largest volume waste generated by the oil industry is produced water. In offshore operations, produced water is treated to remove dispersed oil and is disposed of overboard in accordance with regulatory guidelines. In most onshore operations, produced water is treated and injected either for disposal or for waterflooding operations for secondary oil recovery. Produced water treatment technologies are not discussed in this report.

In Indonesia, most of the E&P wastes (e.g. drilling muds and oily sludges), except treated produced water, are categorized as hazardous and toxic wastes (B3 wastes). In offshore operations, treated produced water meeting regulatory guidelines (oil content < 50 ppm for new installations and 75 ppm for existing facilities) can be discharged overboard.

In the U.S., the E&P wastes are exempt from Federal regulation as hazardous wastes under Resource Conservation and Recovery Act (RCRA) Subtitle C. Only waste streams that are unique to the industry qualify for exemption from Subtitle C. Industrial wastes generated by the E&P industry (such as solvents, paint etc.) are not exempt from RCRA.
Short Term Gas Demand Forecasting Based on Artificial Neural Network
Authors: Sato Ritsuo , Miura Kazuyoshi
Published: December 2007

Teikoku Oil Co. Ltd. (TOC) and NKK Corp. established a joint pilot project in 1994 in order to provide pipeline application and evaluation of NKK's gas hydraulic simulation engine (GASTRAN) and to co-develop a Demand Forecasting Model (DFC). When the pilot project finished in March 1997, a commercial system, called Support Operation and Monitoring Application of Pipeline Simulator (SMAPS), was installed in TOC's operation center.

The DFC, which is based on an artificial neural network architecture, has several advantages for sales forecasting especially as several dozen delivery points that have different sales patterns are connected to the pipeline network. The results from DFC can be easily used for scenarios in off-line simulation to predict future pipeline situations when it is attached to the SMAPS system. It automatically assists the pipeline operator by reducing his workload and evaluating operation plans.
Reducing Contaminant Uncertainty from First Principles
Authors: Frens Ante M.
Published: December 2007

Contaminants in gas reservoirs such as CO2 and H2S have large impact on field development. Although the contaminant concentrations are usually determined during the appraisal of a field, their distribution across the field often remains a key uncertainty with significant impact on the development cost (e.g. through the choice of materials for wells and facilities.)

In this paper we present an innovative approach to determine the distribution of two gaseous contaminants (CO2 and H2S) in different reservoir zones using the fundamental equations for diffusion. In the offshore carbonate gas field, that we describe in this paper, strong variations of CO2 and H2S levels in two of its three reservoirs zones were measured during appraisal of the field. The contaminants originated from thermo-chemical sulfate reduction deep below the reservoir and migrated through the aquifer into the reservoir build-up. The paper addresses two key uncertainties, which have great impact on the development planning:the contaminant levels of the third (deepest) reservoir zone which were expected to be higher than the levels encountered in the other zones;the risk of a contaminant level increase as a result of the liberation of dissolved contaminants from the aquifer when the reservoir pressure drops

Making use of the contaminant generation model and Fick’s 2nd law we determined the contaminant concentrations in the third reservoir zone. On the basis of that result we also show that an increase of contaminant levels as a result of the decrease of the contaminants solubility in the aquifer is no risk in this field.

These results allowed us to tie down these key uncertainties so that a significant cost saving for our wells and facilities could be obtained.
Application of EOS for Multi-component System Containing Heavier Hydrocarbons and Impure Components
Authors: Fujinaga Yoshinobu , Raijo Tsuyoshi , Fujita Kazuo
Published: December 2007

This paper presents effects of pseudoization of heptane-plus (C7+) component through the Constant-Volume-Depletion (CVD) process and influence of heavier fractions on phase behavior around a wellbore using a two-dimensional, two-phase compositional simulator of radial geometry. We investigated retrograde condensation behavior focusing near a producing well. It depends on selection of pseudo-component whether accurate phase behavior predictions can be obtained. Then we could predict more accurate phase behavior around a well in the reservoir by pseudoization and two-dimensional compositional simulator. We show several calculated results for cases where pseudo-components and other properties were changed.
Shale Stability: Drilling Fluid Interaction and Shale Strength
Authors: Lal Manohar
Published: December 2007

This paper presents main results of a shale stability study, related to the understanding of shale/fluid interaction mechanisms, and discusses shale strength correlation. The major shale/fluid interaction mechanisms: Capillary, osmosis, hydraulic, swelling and pressure diffusion, and recent experimental results are discussed. Factors affecting the shale strength are discussed, and a sonic compressional velocity-log based correlation for strength is proposed. Recommendations for modeling and improving shale stability are described, based on the current understanding of shale stability.
Water/Gas Shut-off Candidates Selection
Authors: Kabir A. H. , Bakar M. A. , Salim M. A. , Othman M. , Yunos A.
Published: December 2007

Selecting water/gas shut-off (WGSO) candidates with proper understanding is a critical step which influences outcome of any WGSO effort. Quite often an inexperienced engineer is perplexed by the task of having to find candidates for water/gas shut-off applications, whereas he/she has little idea as to where to start. He/she gets even more confused by selection criteria suggested by various authors, which aren't very clear.

In this paper a systematic approach for finding suitable candidates for WGSO applications is presented. Several techniques of WGSO candidate pre-screening are discussed. A step by step procedure which takes the engineer through a clear thinking process is suggested. WGSO candidates selection is best treated as part of his/her routine wellbore utility study (yearly event). Starting point is to conduct a well and reservoir performance review for the entire field based on all the data in hand. A list of required basic data which are helpful in this review is provided, as much of which as possible should be collated prior to this candidate selection exercise. Guidelines for further diagnosis to firm up WGSO candidates is also provided. Outcome of this study is a comprehensive list of all potential remedial work, of which WGSO is a subset. Having a complete picture of the well and reservoir performance helps an engineer understand reservoir fluid movement mechanism and therefore objectives of any remedial work becomes very clear. Then the engineer can review all products and services available in the market and can choose the most appropriate solution. Without a proper diagnosis and clear understanding of reservoir fluid flow pattern, any attempted solution will only be a guesswork and success rate will remain low.
Interwell Log Correlation Using Artificial Intelligence Approach and Multivariate Statistical Analysis
Authors: Lim Jong-Se , Kang Joe M. , Kim Jungwhan
Published: December 2007

A new approach to automated interwell log correlation using both artificial intelligence (AI) and multivariate statistical analysis is described. Correlation of wireline logging data is on the basis of a large set of subjective rules for pattern recognition that is intended to represent human logical processes. The data processed are the characteristics of the shapes extracted along log traces by object-oriented programming (OOP). Correlation of zones between wells is made by rule-based inference program. This method has the advantage over the conventional methods due to the capability of handling the shifting, thickening, and thinning strata in interwell correlation. Use of statistical techniques can obtain more reliable correlation results for complex geologic formation. The efficient and reliable pattern recognition for correlation can be established by using the first principal component log, since it has the largest common part of variance of all available well-log data. In addition, the electrofacies derived by selecting, weighting, and combing the multivariate well-logs can be used as an important information of lithology identification for more reliable correlation. Correlated results with logging data in the Korea Continental Shelf and oversea field show that this method can be used to make it more reliable and efficient to interwell log correlation rather than the traditional methods in which only one approach was adopted. It can be applied as an effective tool in planning the development and production strategy of the field.
A New Approach to Study on Thixotropic Properties of Waxy Crude Oils from Dragon and White Tiger Fields Offshore Vietnam
Authors: Thuc Phung Dinh , Van Bich Ha , Son Tong Canh , Vugovskoi V. P. , Le Dinh Hoe
Published: December 2007

In production and transportation of waxy crude oil as well as in practical Rheological studies of non-Newtonian liquids, it is very important to find and characterize its thixotropic properties. There are some ways to study this phenomenon, but nowadays the existing equations still can not quantifiably describe the time-dependent behavior of thixotropic liquids with acceptable accuracy using in this case an exponential or hyperbolic functions.

The authors have conducted the screening studies on rotational viscometer Rotovisco RV-20 with different kinds of waxy crude oils from JV "Vietsovpetro" fields offshore Vietnam. Based on the received experimental data and its analysis the authors have proposed a new equation showing a very good agreement between experimental and calculated data (the average deviation is less than 2%). The general time-dependence of shear stress at constant shear rate can be much more precisely expressed.

A new idea "the measure of thixotropicity" of liquids at given shear rate and temperature is also proposed to characterize the properties of thixotropic liquids.
A Viscoelastic Model for Polymer Flow in Reservoir Rocks
Authors: Garrouch Ali A.
Published: December 2007

In this work, steady-state flow experimental data have been analyzed for two commonly used polymers representing two generic classes: polysaccharides (xanflood), and partially hydrolyzed polyacrylamides (pusher-700) flowing inside bead packs and Berea sandstone. Oscillatory flow measurements have been used to compute the polymer solution's longest relaxation time (θf1). Steady-state flow experimental data for the two polymers combined with measured polymer viscous properties have been converted to average shear stress-shear rate data inside porous media. An average power-law exponent (n̄) is therefore obtained for the polymer flow inside the porous medium. Using θf1 and n̄, rock permeability (k) and porosity (ϕ) and fluid flow velocity (u), a dimensional number Nv (viscosity number) is calculated, and found to strongly correlate with the pressure gradient inside porous medium. This correlation is the basis for defining a viscoelastic model for polymer flow in porous media. The capillary-tube model is found to be adequate for only flow of viscous polymers with insignificant elasticity.