bluuebunny/crossref_metadata_2025 huggingface dataset:
Reservoir Flow Units: A Comparison Between Three Different Models in the Santa Barbara and Pirital Fields, North Monagas Area, Eastern Venezuela Basin
Authors: Porras J. C. , Barbato R. , Khazen L.
Published: December 2007

The North Monagas Area presents apparently homogeneous thick sand bodies in the producing section. These sands, some in the order of hundreds of feet, have been until recently considered as single flow units. However, different production scenarios have indicated the presence of distinct flow units with particular petrophysical characteristics within each sand. Several definitions and techniques have been applied to determine flow units. In this study, flow units are defined as sediment intervals that maintain a similar relation between their petrophysical properties such as porosity, permeability, water saturation, pore throat radius, and storage and flow capacity, and that differ from the petrophysical characteristics of the intervals immediately above and below. Three different methodologies were analyzed and compared with the purpose of determining their similarities and divergences. The first method is derived from the sedimentological description of cores, using grain size as the main factor. The second method applies empirical equations based on pore throat radius an its relation to flow capacity, and their use in the determination of petrofacies or rock types, whereas the third method is based on a systematic model which uses the concepts of mean hydraulic radius and flow zone indicators to determine hydraulic units. The definition of flow units allowed a better petrophysical characterization of the field and provided better judgement for the selection of production and injection intervals.
Production of Heavy Oil Via Core Flow
Authors: Bannwart A. C. , Vanegas Prada J. W.
Published: December 2007

This work proposes a new technology for heavy oil lift by using the core annular flow pattern (shortly "core flow"). This flow arrangement can be induced through the lateral injection of relatively small quantities of water, in order to get a lubricated oil core along the pipe. With this objective in mind, an experimental apparatus was built and tested at laboratory scale (1 in. vertical pipe) using a 17.6 Pa.s, 960 kg/m3 oil and water at room temperatures. The frictional pressure drop was reduced by 700 to 2000 times with respect to single phase oil flow and is of the same order as the flow of water alone at same total flow rate. The total pressure drop was reduced by 45 to 150 times with respect to single phase oil flow and the optimum water-oil input ratio was in the range 0.07 – 0.5, depending on the superficial velocity of the oil.
Evaluation of Production Methods in the Morichal Heavy oil Reservoirs
Authors: Boardman D. W. , Lopez S. , Pineda F. , Zerpa L.
Published: December 2007

A thermal numerical simulation model has been used to history match an area of the Morichal-01 reservoir where cold production from horizontal wells and a continuous steam injection pilot project have been undertaken, allowing the efficiency of these processes to be assessed. The production performance of 47 horizontal wells in the field has been analysed analytically, and also modelled in the simulation; the study defined average well performance and quantified the potential gain from improving the artificial lift. The high reservoir pressures mean that sufficient reservoir energy is available to make cold production from horizontal wells the preferable option.

Multi-lateral well productivities have been evaluated to show the potential cost savings from introducing this technology, if artificial lift efficiency can be improved.
Improved Swi Determination and Producibility Estimation Using NMR, Dielectric and Induction Array Systems in San Jorge Basin
Authors: Breda Eduardo , Minetto Carlos
Published: December 2007

The productivity in shaly-sands and sand-tuffaceous reservoirs are adversely affected by changes in permeability and porosity due to varying cementation material, authigenic clays and dual porosity system. When those reservoirs contain viscous oil in presence of strongly fresh water, high capillary forces, the Swi determination and Producibility estimation become more complex.

That is the case in San Jorge Basin where the oils are frequently biodegraded, the water has low salinity and mainly accumulated in fluvials or lacustrine sandstones. The problem is even more pressing when oil viscosity varies within a hydrocarbon column or from zone to zone when attempting to commingle multiple zones.

To reduce those petrophysical uncertainties a model combining the response of NMR, Dielectric and Induction Array tools with new algorithms for T2 Inversion and Film Model was used.

The NMR Swi was compared with core and from these data, a new permeability index was derived. The Dielectric and Induction Array systems control the invasion and the heavy oil presence, improving the accuracy of productivity predictions and increasing hydrocarbon production.

This paper presents the applied model and successful results obtained in San Jorge Basin where the enhanced characterization of the reservoirs allowed us to increase the oil production after hydraulic fractures from 5 to 20 times initial rate.
Oil Production and Learning
Authors: Vargas de Alamo N. , Brandt R. , Paz F. , Gullón R. , Garcia A.
Published: December 2007

The basis for the change in Petróleos de Venezuela (PDVSA) in its Business Production Unit, is a very simple one: to reach the target of production of fluids, shown in PDVSA's Business Plan. It is necessary to duplicate the productivity of the technical personnel in charge of executing the plan.

The company executes an ambitious plan for developing and maintaining competencies, addressed at an approximate population of 2,500 professionals in the areas of petroleum engineering, and geosciences, defined as key positions in the core areas.

In order to attain this level of technical excellence, a complete learning plan, based on the interaction of several mechanisms, has been formulated. These are Integrated Training Programs, at a Basic, Intermedate and Advanced Level, as well as Special Training Programs, such as the program for the Formation of Seismic Interpreter and Petrophycisists. At the same time, it has implemented an ambitious plan for Fellowships for post graduate studies and technical assignments, in companies and international institutions of well-known technical level. Other types of training are also explored, such as Virtual Learning Programs and Self-development and On-the-job training. There has been an important investment of capital in the physical infrastructure, where these practical training programs in Integral Reservoir Management are carried out. The most relevant results obtained since the Competence Development and Maintenance Management in the Production Business Unit of PDVSA was created after the organizational transformation undergone in January 1998, are presented at the end of this paper.

This significant advance in learning strategies will provide PDVSA with cadres of highly qualified technical personnel able to perform at the levels of efficiency required in the present Business Plan.
Characterizing Permeability Distributions with Integral Autocorrelation Estimators
Authors: Savioli G. B. , Saccomano A. F. , Bidner M. S.
Published: December 2007

Permeability distributions of very heterogeneous reservoir rocks are analyzed by applying different autocorrelation estimators: the classical semivariance estimator (CSV) and two moving window semivariance estimators (MW1 and MW2), introduced by Li and Lake1 in 1994. The goal of this work is to compare the ability of Simulated Annealing (SA) to represent actual heterogeneity, when each one of the three estimators is introduced in the objective function. The objective function is minimized by the Metropolis algorithm. With that aim, the generated image of permeabilities is compared with core measurements. Although MW1 and MW2 are more robust and resistant than CSV, they only present minor advantages when introduced into SA to describe permeability distributions.
Effective Integration of the Core Analysis and Wireline Datasets-Using a New Core Analysis Data Suite and New Software
Authors: Theologou P. N. , East R. D. , Curtis A. A. , Boult P. J. , Drake A. M.
Published: December 2007

Core analysis information is considered one of the cornerstones of formation evaluation. However, there seems to be general consensus that more could be done with it, both in the scope of the petrophysical data obtained and how it is used. In recognition of this, a suite of methods have been developed that provide a ‘new’ extended core data set, and software has been designed expressly for the interpretation of core data.

Historically, there has been a gap in the services provided by core analysis laboratories. Routine core analysis (RCA) provides core plug measurements such as porosity, permeability, fluid saturations, grain density and whole core gamma at high sample frequency and low cost. However, this data has limited interpretative potential. On the other hand, special core analysis (SCAL) provides a range of information with high interpretative potential, but at a low sampling frequency, primarily due to the cost and extended time frames associated with gathering the data.

A new data set was designed to compliment the current (RCA) data set, significantly extending its interpretative potential. The additional measurements performed are total, effective and furnace porosity, capillary pressure versus water saturation curve, surface area, core plug spectral gamma and an extended sample description. This new information fills the gap that currently exists between RCA and SCAL data, by providing significant interpretative potential at a high sampling frequency and in a reasonable time frame.

The computation of core-based or core-enhanced petrophysical interpretations has also been hampered by the lack of software designed expressly for modeling core data. Most petrophysical packages are decidedly log-centric, which has limited the effective integration of core and log data. Much core data processing is performed using spreadsheets, with inherent data integration and transfer limitations. To redress the balance, a core interpretation module designed to handle both the new data suite and existing core data, has been developed within a main-stream log analysis software package.

Applications using the new data suite include calibration of petrophysical parameters, the estimation of Qv profile from surface area data, the independent assessment of water saturation through the reservoir, and the estimation of initial reservoir flow properties at production start-up. The final outcome is that core analysis becomes truly a parallel formation evaluation discipline. In order to illustrate the core-log integration capabilities of the package, case studies are presented.
Pressure Response of Layered Reservoirs with Crossflow in the Presence of Gravity Effects
Authors: Savioli G. B. , Bidner M. S. , Cocco M. J. , Jacovkis P. M.
Published: December 2007

This paper deals with the understanding of well-test response in flow through bounded, heterogeneous reservoirs, in the presence of gravity effects. To generate these insights, we solve the two dimensional flow of oil by finite differences. The resulting system of linear equations is solved by a method based on Taylor Series of Matrix Functions (TSMF). The numerical simulator is applied to study the flow in a two-layer system with crossflow. The effects of vertical permeability and gravity are studied and insights into how these effects would alter well-test interpretation presented.
Experimental Study of Two Phase Pumping in Progressive Cavity Pumps
Authors: Martin A. M. , Kenyery F. , Tremante A.
Published: December 2007

Multiphase pumping has consolidated itself as the state of the art technology in crude oil transport for declining and marginal fields. Several types of pumps have been applied or developed for such service, opening a new research trend worldwide.

In this research we studied the progressive cavity pump performance with two-phase flow. Our aim was to obtain the pressure and temperature profiles along the pump's stator, and to observe its behavior under different sets of variables such as gas void fraction, rotational speed and Ap. The knowledge that can be acquired will be useful to estimate how flow conditions can be affecting the pump's life and the smoothness of the pump performance.

The results showed that for single-phase flow at low Ap the maximum pressure is not located at the pump outlet as it would be expected. The pressure distribution in the pump with two phase flow is completely different to the latter case, being found that within the pressure range of the experiment the cavities are kept sealed almost along the whole pump. For any point of operation the maximum temperature is found in the intermediate stages.
Use of Automatic History Matching and Geostatistical Simulation to Improve Production Forecast
Authors: Portella R. C. M. , Prais F.
Published: December 2007

The development of automatic history matching techniques is receiving much attention recently. The methods are becoming increasingly faster making practical applications possible. In general, these methods provide a single solution that matches the observed data, but as the solution of inverse problems is not unique, there is no guarantee that production forecasts made with the adjusted model will produce good results. Thus, it would be desirable to know the confidence interval of the adjusted model. The methodology presented in this paper combines a history matching technique with geostatistical modeling to provide equiprobable reservoir images that take into consideration production data. The method starts by doing an automatic history matching using existent production data. The automatic history matching technique used in this paper is based in simulated annealing, and it uses pilot points to reduce the number of adjusting parameters. The resulting adjusted model provided by this technique is then used to generate geostatiscal realizations. Using values of the pilot points and the original existent data as conditioning points, several geostatistical images are generated. Then, these images are used to obtain the confidence interval of production forecasts by performing a flow simulation in each one of them.

Although the computational cost of the methodology is high, the information about the uncertainty of the production forecast that it generates compensates the additional time necessary to obtain the results. In addition, the final reservoir images obtained with this technique will be much closer to the real reservoir than images generated using only static information of properties in the wells. The paper also shows a complete example where the adjusted parameter is the permeability field of the reservoir. This methodology could be applied with any optimization method, and it provides an excellent way to access production uncertainty.
Pore Network Model of a Bubble-Driven Drainage Process
Authors: Alvarado V. , Rodríguez A. A.
Published: December 2007

A network model has been developed to study a drainage process driven by the growth of gas bubbles in the span of viscous liquid in a disordered lattice. This medium is a two-dimensional network made up of spherical pore-bodies connected by cylindrical pore-throats. The pore-bodies act as fluid containers, while the pore-throats control fluid pressure drops and capillary pressure in the presence of liquid-gas interfaces. The fluid, at the initial stage of the simulation, is a homogeneous mixture of gas in solution and an incompressible liquid. Two stages of the process are included: site activation and growth of bubbles. Site activation occurs when the pressure of the liquid allows the release of trapped gas at the solid surface crevices. Growth takes place by bubble expansion that drives the liquid out of the system. Two pressure boundary conditions for the network are considered. The first one consists of a sudden pressure drop at the external lateral boundaries (and either periodic or no-flow boundary conditions at the top and bottom) from the initial equilibrium condition, which allows simultaneous activation of bubbles. A second condition is a linear pressure decline at the lateral boundaries, which leads to progressive site activation. We show gas bubble size distribution as a function of time and position. It has been observed a very strong dependence on the studied boundary conditions.
Laboratory Study of Gravity Drainage Mechanism in Fractured Carbonate Reservoir-Reinfiltration
Authors: Sajjadian V. A. , Danesh A.
Published: December 2007

In a well fractured reservoir that has a gas cap, after commencement of production the gas cap expands and the gas-oil contact (GOC) in the fracture system descends. The oil contained within the matrix of the gas invaded zone begins to drain down into the fracture system and into the lower matrix blocks, due to the force of gravity. Some of the oil that is drained out of the upper matrix blocks can reinfiltrate into the lower matrix blocks from the top or side surfaces and can flow down through the areas of contact between blocks.

In this study, data on a set of experiments that center on reinfiltration process are presented. The experiments cover fully saturated and desaturated blocks in vertical and inclined positions. The results of our experimental works reveal that the reinfiltration process depends mainly on the physical properties of the matrix block, the rate of oil supplied, and the drainage stage of the block.

When oil is trickled at the top of a desaturated block, initially due to an extra capillary pressure gradient the infiltration rate can be higher than the maximum drainage rate of the block. After some time the rate of the drainage approaches that of the infiltration and an almost steady state flow is established. At this condition, the lower portion of the block could drain oil, while the upper portion could be under infiltration process.

When the oil is directly supplied on the top of the vertical fracture, its crossflow from fracture to the adjacent matrix is demonstrated. In other words, under certain conditions the high conductivity vertical fractures are not necessarily the primary flow path of the supplied oil.

The purpose of this study is to provide a basic understanding of reinfiltration process in fractured porous media.
A Sand Erosion Model for Volumetric Sand Predictions in a North Sea Reservoir
Authors: Papamichos E. , Malmanger E. M.
Published: December 2007

Volumetric sand production data from a North Sea reservoir are interpreted with respect to the applied drawdown. Two sand rates are identified, one related to the increase of the drawdown and one to the magnitude of the drawdown. A sand erosion model is presented and used for predicting the field data. The model results compare satisfactorily with the field observations.
The Diagnosis, Well Damage Evaluation and Critical Drawdown Calculations of Sand Production Problems in the Ceuta Field, Lake Maracaibo, Venezuela
Authors: Vásquez H. A. R. , Sánchez D. M. S. , Yánez R. L. , Poquioma W. , Rampazzo M. , Chirity K. El
Published: December 2007

A geomechanics based methodology was utilized to analyze sand production problems as well as the amount of damage caused to the wells of the Southern Area 2 sector of the Ceuta field in Lake Maracaibo, Venezuela. Sand production in this field was not originally expected since the reservoir is composed of a well consolidated sand at depths larger than 16,000 feet and with rocks having an unconfined compressive strength larger than 6000 psi. Geomechanically speaking, sand production is caused when the destabilizing stresses on the formation are larger than the resistance due to formation strength. However, certain well operations can affect the destabilizing stresses as well as the formation strength. Therefore geomechanics must be used together with proper operational procedures because many operational details can also have a profound effect on the occurrence of sand production. One of the most important factors has to do with the production practices involving proper choke sizes and excessive choke changes. Sand production data gathered in the Ceuta field was analyzed using a geomechanical framework of understanding to predict well damage and problems during choke changes. The data defines 3 different stages of sand production for wells in this field. Each stage has a particular behavior and different problems associated with them. The sand production data was integrated together with the fluid production data to calculate the amount of accumulated sand production. A simple spherical model was developed to calculate cavity size around the casing utilizing the accumulated sand production. It was found that a well could produce large quantities of sand before total well failure. Total well failure appears to be related to the size of the cavities around the casing which leave it unsupported and also to erosive damage to the casing done by the sand laden fluids. The sand producing data was then used to diagnose the stage at which the sand production problem occurs and to change choke utilization practices in order to minimize sand production. Special laboratory geomechanical tests on core from the area and full wave sonic logging information was used to generate a model which calculates the critical drawdown for the problematic sands. Critical drawdown control has been the solution for most wells. Some other solutions such as hydraulic fracture and highly deviated wells in the correct direction have also been utilized.
Case History: Well Completion and Servicing Strategies for the Hibernia Field
Authors: Wylie Glenda , Maier Rod , Shamloo Said , Huffman Micky , Downton Neil
Published: December 2007

Offshore field development includes not only planning for appropriate well completion designs but also implementing in such a manner that production and economic goals for all stakeholders are realized. Consideration must also be given to operational support functions so that their administration will meet the project needs without compromising environmental, regulatory or safety standards. Often, a multidiscipline team approach offers the best method for developing the solutions needed to accomplish all the objectives. In this paper, Hibernia Management's approach to well development, completion and servicing strategies are discussed. Initial completion strategies were required to meet the designated design criteria of maximum well deliverability, minimal well maintenance, well servicing costs, and finally, minimal overall field-life-cycle costs. To comply with these stringent requirements as well as future needs, the downhole configuration would have to facilitate future non-rig workovers, recompletions or redrills, and have the flexibility to allow incorporation of future technological advances or changes in reservoir management.

In reviewing all options, minimizing overall field-life-cycle costs and the number of potential workovers were to be given primary consideration. Also of significant importance was the need to provide a zonal recompletion method as it was felt that the need for selective isolation of different zones would be needed to maximize recovery throughout the life of the wells. Completion strategies, the completion configuration, pre-installation shop tests, personnel training, completion servicing considerations and other challenges such as a "green field site" and rig requirements were reviewed; from these analyses, operational strategies were developed.

The initial completion installations were successful. The first two wells flowed approximately 40,000 BOPD and are Canada's highest producing wells recorded to date!
Development of a True 3D Hydraulic Fracturing Simulator
Authors: Yamamoto K. , Shimamoto T. , Maezumi S.
Published: December 2007

The recent development of horizontal and deviated borehole drilling technology in oil and gas wells requires hydraulic fracturing simulators which can take the three-dimensional formation of fractures into account. The authors have developed a fully coupled modeling of fracture opening and injected fluid flow for the three-dimensional formation of hydraulically induced fractures. The simulation can deal with the entire process of hydraulic fracturing including the post-shut-in process. A three-dimensional Displacement Discontinuity (DD) formulation for an elastic medium is used to model the relationship of fracture aperture and stress around the fracture. This formulation allows the simulator to deal with three-dimensional fracture propagation including bending and twisting of the fracture.

Fracture propagation based on the linear elastic fracture mechanics model, non-Newtonian behavior of the fracture fluid, and proppant transportation are modeled in the simulator. Fracturing processes including the post-shut-in process are calculated so as to satisfy the equilibrium of injected fluid volume, fracture volume and leak-off volume.

The numerical fracturing simulator can be used as a platform for studying the behavior of complicated hydraulic fracturing processes, and as a tool for the optimal design of hydraulic induced fractures.
Stochastic Reservoir Modeling of Sand GS - 8: Gandhar Field, Western India
Authors: Jain A. K. , Mathur A. D. , Taneja H. R.
Published: December 2007

Gandhar field in western India has multiple sandstone layers of Middle Eocene age. These layers, designated as GS-1 (bottom) through GS-12 (top), are separated by distinct shale markers, thus promoting different layers to reservoirs of separate identities.

GS-8 sand of this field, which is the focus of present study, has traditionally been an oil producer. A recent well has now produced gas from the bottom part of this sand. This has created doubts about the presence of a local gas cap, about the fluid content of GS-8 and its distribution and about the vertical and lateral continuity of the permeable facies.

The study addresses these issues with an objective to frame reservoir description of GS-8 in order to evolve an effective exploitation strategy. It is based on stochastic modeling of electrical log data as fundamental input.

Probability distribution maps of log derived lithofacies and their petrophysical characters have been prepared, based on average log parameters at one meter interval, starting from the base of GS-8 upto a height of fifteen meters. These distributions help visualize spatiotemporal evolution of the whole GS-8 unit. Fifteen meter thick pack of these maps, placed on top of one another in stratigraphic order, has further been sectioned along closely spaced north-south and east-west lines. These sections have been found to be of great use in displaying the micro-stratigraphic sequences and delineating various flow units of GS-8 layer.

The sections reveal that the sand bodies are isolated, and are encased within the adjacent shale layer in many pockets, giving a complicated picture of the reservoir. They also clarify that, by and large, the GS-8 unit is divisible into two sub units, GS-8A (lower) and GS-8B (upper). The deposition of these sub-units is area specific, and they are separated by a low porosity zone.

Another revealation of the study has been that GS-8 layer, as a whole, is not a closed system insulated by a shale layer, and at places it is connected with overlying layer GS-9. The study has helped extend chrono-stratigraphic boundary between layers GS-8 and GS-9 at those places (which otherwise had been difficult), within lithofacially homogeneous reservoir facies.
Application of Grey System Theory to Gas Pool Prediction of 3D Seismic Data prior to Drilling
Authors: Changrong Lin
Published: December 2007

Using 3D seismic data to predict the oil and gas situation before drilling is of benefit to improving the ratio of successful drilling. Owing to the complex situation of petroleum geology, especially in cases of limited data and uncertain information, a novel solution is necessary.

In this paper, a novel technological theory, grey system theory, is introduced. The investigation of the stratum containing gas underground is completed via grey modelling, grey prediction and grey relational analysis. So, a quantitative grey procedure is introduced into the field of petroleum geology, normally a field investigated with qualitative description.

Grey system theory, was created by professor Deng Julong in 1982. A number of projects in different fields have been successfully completed using grey system theory, procedures and concepts. Here, the grey system theory is successfully used in a number of wells prior to drilling, The results of experiments are very satisfactory --- a total of 16 wells in 10 structures are predicted prior to drilling. The ratio of successful drillling is over 87%. Therefore, the grey system theory and methods attract attention for predicting and analysing oil and gas status before drilling.
Planning of Deepwater Drilling Operations with Aerated Fluids
Authors: Nakagawa E. Y. , Santos H. , Cunha J. C. , Shayegi S.
Published: December 2007

Although underbalanced drilling (UBD) has been used for many years, with more than 11,000 wells drilled underbalanced in Canada and the USA, this technique has been almost exclusively applied to onshore fields. Despite a few experiences offshore, questions related to safety, logistics, and equipment placement have kept offshore UBD restricted to fixed platforms or jack-up rigs. Nevertheless, the industry trend towards offshore deepwater production has made it imperative to make this technology technically and economically viable for use in floater units as well.

This paper describes current efforts being made by a group of companies involved in a Joint Industry Project (JIP) focused on planning and drilling a deepwater offshore well from a semi-submersible platform using nitrified fluid. Although the well will not be drilled underbalanced for this first well, it will be the first well to be drilled from a floating vessel using a gasified fluid.

The main issues addressed in the project include: field data analysis, drilling hydraulics and cuttings transport experiments and modeling, software development and validation, formation damage experiments and modeling, wellbore stability failure mechanisms, operational procedures, safety issues, equipment development and/or conversion and benefits quantification for the process. Several of the key issues are discussed in this paper.
Convergence of Key Technologies in Multilateral Well Construction
Authors: Ben Lim S. B. , Good Alan
Published: December 2007

The authors in this paper attempt to propose a model for identifying and selecting key technologies that would add value to the return on investment on a Multilateral well. The last few years have seen the proliferation of Multilateral (ML) wells in the Asia Pacific region and elsewhere in the world. On a parallel front, the oil industry has experienced the introduction of key technologies such as geosteering, rotary steerable "automated" drilling tools, sealed junction technologies, non damaging drill-in fluids, re-entry access completion equipment in development projects worldwide. In conjunction with the development in junction classification and junction construction, it has been noticed that these key technologies in areas of drilling, completion and well planning are increasingly being applied to the construction of Multilateral wells.

This paper traces the historical outline of the technology development in Multilateral wells, and it documents the milestone introduction of key technologies that will greatly enhance the return on investment in a Multilateral well. The Authors in this paper will propose a model for identifying the technology needs and the potential enhancement in cost savings for applying key technology. The benefits and cost effectiveness of these technologies are discussed in this paper, and the inevitability of Multi-lateral technology converging with other key technologies are highlighted.
Stochastic Modeling for the Heterogeneous Anisotropic Reservoir System by Using Geostatistics
Authors: Lee Dongseong , Kang Joe M.
Published: December 2007

We present a method to characterize a heterogeneous anisotropic reservoir by integrating both core data and well testing data.

To characterize a heterogeneous anisotropic reservoir, we introduce coordinate transformation which convert the anisotropic reservoir into the isotropic one. Anisotropy can be expressed by grid block permeability or correlation length or both of those. For each case coordinate transformation function is developed respectively. On the transformed domain simulated annealing is employed to optimize the permeability field. Then final heterogeneous anisotropic permeability field is obtained by inverse transformation. To predict the breakthrough time, the simulation of water flooding is performed stochastically on the several types of characterized anisotropic fields.

The results show that trend of pressure and permeability image of the characterized field is close to that of the base field. The breakthrough time can be predicted more accurately within a confidence interval when water flooding is simulated on the characterized heterogeneous anisotropic reservoirs. The proposed method can reduce the reservoir uncertainty significantly since both well testing data and geological data are used.
Application of Spectroscopy C/O Logging in Tempino and Bajubang
Authors: Mas C. , Adi S. , Dewati R.
Published: December 2007

C/O logging has been used successfully to evaluate feasibility of water flood program in the 60 years old oil fields Tempino and Bajubang. A total of 25 wells were surveyed during April 1994 to August 1995. Combined with the neutron logs and swab tests, the logs were used to monitor behind casing saturation for water encroachment, confirm the existence of gas cap and solution gas drive, confirm that the fault blocks are isolated, substitute for the lack of open hole log data and lithology evaluations and to evaluate the potential of water supply sand. Results of evaluations in Tempino and Bajubang are in the implementation process. Positive responses are observed in the fault blocks where the water flood has been fully implemented. Logging program design is critically important to the interpretation process. Recommended procedures are discussed.
Advanced Horizontal Well Production Logging – An Australian Offshore Example
Authors: Carnegie A.
Published: December 2007

A production log (PL) was run in a horizontal well in a high permeability field offshore Australia. The well was completed with slotted liner and ECP's. The main answers sought by the log were: the location of any unproductive sections of the well bore, a measurement of the inflow profile, a check on the trajectory of the well (as derived from measurement whilst drilling), and an understanding on whether flow was occuring between the ECP's and the formation. This information helps answer the following important questions: a) What should the lengths and trajectories be of horizontal wells drilled in the future life of the field? b) Can such trajectories of such wells be drilled with sufficient depth accuracy, c) What are the optimum clean up strategies for these wells? d) Should these future wells contain ECP's? e) How should the productivity be optimised, of the existing wells in the field (including the one logged)? The well only flowed oil to surface. But previous experience showed that water sumps and gas traps would probably exist, and potentially cause multi-phase flow conditions to prevail down hole, thereby complicating the responses of sensors. For example, stagnant or circulating water could completely distort the spinner response. A further complication was that flow could be occurring between the liner and the formation. Therefore, a logging approach was chosen which had previously been proven to be able to deal with multiphase flow in horizontal wells completed with slotted liner. The approach chosen relies on combining traditional PL sensors (spinners, pressure and temperature) with recently developed sensors, which image down hole flow, determine the holdups of oil water and gas inside the wellbore, measure the velocity of water, and provide knowledge of holdup and flow in the liner to formation annulus. To save rig time all sensors were deployed on one tool string, which was conveyed by coiled tubing.

Large amounts of data were generated from each sensor. These were integrated to provide answers to all the questions mentioned above – these would almost certainly have been left unanswered or answered incorrectly if the individual sensors had been interpreted in isolation from one another. Additionally, some surprising results were found. Notably: 1) Apparently small downward shifts of approximately 1 metre in sections of the trajectory towards the toe could be causing significant productivity impairment from these sections, 2) It is possible to have almost no drawdown inside the liner, whilst having significant production from the liner to formation annulus – this last result is associated with sections of liner which have remained impermeable since the time of completion.
Application of Seismic Inversion and Special Processing Techniques to Fracture Distribution Prediction
Authors: Chen Jun , Song Xinmin , Yao Fengchang , Cao Hong
Published: December 2007

Although there are some advances in geophysical methods of identifying subsurface fractures (for example, imaging well logs, cross-hole tomography and seismic reflection analysis of shear wave), they are generally quite expensive and commonly are not economically justifiable in mature, relatively low-production reservoirs. This paper presents an integrated method of recognizing subsurface fractures mainly based on conventional geophysical information (conventional well-logging and compressional wave data). The research thinking is to first extract lithology and fracture information from conventional well-logging data according to the responses of well logs to all kinds of geological features, then reconstruct pseudo-acoustic curves by transforming lithology and fracture information into acoustic information, and complete seismic inversion under well quality control or well constrained inversion. Through research and practice of certain fractured reservoirs, a few methods are summed up as follows. (1) Lithology control on fractured distribution are well known, fractured zone can be indirectly predicted by means of seismic inversion detecting lithology distribution. The applications of the method in carbonate and conglomerate reservoirs have gained good effects. (2) It is certain that seismic data mainly contain lithology and fracture information in very low-permeability fractured reservoirs, fractured zone can be identified by comparison of seismic inversion results from lithology and fracture information.
Tapis - New Opportunities from a Maturing Field
Authors: Abdullah Muhammad Aw Yong , Olsen B. S.
Published: December 2007

This paper focuses on how the integration of technologies such as sequence stratigraphy, log analysis, 3D seismic, reservoir simulation and drilling have helped in overcoming the many challenges, and increased Tapis field's reserves by about 30 percent. The work program for realizing these reserves includes rig workovers, infill/step-out drilling from existing platforms, and installation of a new satellite platform. To date, the rig workovers and most of the infill drilling have been completed, and results have been mixed but overall, encouraging. The new satellite platform was installed in third quarter of 1998 and development drilling off this platform is now underway. The experience at Tapis demonstrates the value of looking for new opportunities in mature fields.

The Tapis field is located approximately 210 km (130 miles) off the east coast of Peninsular Malaysia in the South China Sea at water depth of about 64 m (200 feet). The field was discovered in 1969 by the Tapis −1 exploration well and further delineated with three appraisal wells before development drilling commenced in 1977. Five platforms were installed and a total of 90 development wells were drilled as at year-end 1998. Waterflood was implemented to maximize ultimate recovery from the field. Over 47.7 million st.kL (300 million STB) of oil has been produced to date with a peak oil rate of about 12.7 thousand st.kL (80 thousand STB) per day achieved after the initial two years of production buildup. From about the seventh year, the field's production went on a steady decline and reached a rate of about 3.3 thousand st.kL (21 thousand STB) per day after about 15 years of production. In 1993, a multi-disciplinary team consisting of geophysicists, geologists, petrophysicists and reservoir engineers was assembled to identify both near- and longer-term opportunities in the field to mitigate the production decline.
Evaluating the Effectiveness of 3D-Seismic in Northwest Paluh Tabuhan Field: A Case Study
Authors: Basuki Puspo P. , Santoso Djoko , Hendrajaya Lilik
Published: December 2007

The effectiveness of 3D-seismic is controlled by four factors: the physical properties of reservoirs, the seismic frequency content, the field parameter design, and the goals to be achieved, provided that the collected data be processed and interpreted appropriately. By understanding the first and second factors, one can design the third factor optimally, and also estimate the effectiveness of 3D-seismic. This paper proposes a concept of 3D-seismic effectiveness measurement based on the dominant seismic wavelength and the thickness of reservoirs. The concept enables one to estimate the effectiveness of a 3D-seismic project and even to prepare actions to improve the effectiveness. To check the validity, the concept is applied to a case study of Northwest Paluh Tabuhan Field in North Sumatra Basin. The purpose of the 3D-seismic survey in this field was to better understand the detailed geological interpretation which enables one to effectively drain the field and to delineate the extension of the field. Using the above mentioned proposal, it was estimated that the 3D-seismic survey would be 54% effective or 72% conditionally effective. The interpretation of seismic data provided satisfying structural maps, however, it was unable to map the lateral distribution of the objective reservoirs. It was evident that the 3D-seismic data was ineffective in achieving the goal. This ineffectiveness, more specifically the inability of seismic data to show the lateral distribution of objective reservoirs, occurred due to the limited thickness of the reservoirs and the frequency content of seismic data. The results of interpretation meets the estimation derived from the concept of effectiveness. The concept proposed for onshore 3D-seismic survey is applicable to offshore data as well.
Successful Application of Water-Conformance Technology: A Case Study from East Kalimantan, Indonesia
Authors: Hunter Steven , Soetedja Vincent , Rinadi M. , Mitchell Wayne , Gauntt Gary
Published: December 2007

Until recently, excessive water production in this East Kalimantan Field was not considered to present a major problem. The two main reasons for this were (1) adequate water disposal facilities for the water production and (2) the perception that water control treatments would not have a material impact in reducing water production or increasing oil recovery. This paper presents a case study from the Semberah field in East Kalimantan, which shows that with proper problem identification, the use of available technology and placement techniques can significantly reduce water production and simultaneously realize an increase in oil production.
Applications of Carbon/Oxygen Logging in Indonesian Reservoirs
Authors: Fox P. E. , Adnyiana G. , Setiadi I.
Published: December 2007

Clastic reservoirs with waterdrive mechanisms can lead to tricky interpretations in instances where resistivity measurements have little contrast between freshwater- and oil-bearing rocks. Indonesia’s clastic and carbonate environments can provide challenges in reservoir monitor evaluation, especially in the detection of fluid types behind pipe, quantification of reserve depletion, and control of high water production.

Carbon/oxygen (C/O) logging is primarily utilized to determine oil-water saturations and reservoir performance in areas with low or unknown formation-water salinities. The C/O measurement is based on carbon and oxygen reactions with high-energy "fast" neutrons producing characteristic gamma rays. From this measurement, one can distinguish between hydrocarbons (C + H) and water (H + O). This, of course, is a very simplistic model of real-world applications that are complicated by mineralogy, wellbore environmental conditions, and reservoir behavior. Successful applications of C/O logging in Indonesia have included

Identification of oil reserves otherwise difficult to detect Monitoring reservoir depletion Identification of horizontal well placement target Detection of oil-water contacts for conformance treatment applications Inter-reservoir crossflow identification by oxygen activation combined with production logs Oil-saturation analysis for initial well completions when openhole logs are not obtainable Confirmation of steamflood efficiency

This paper presents a few of over 100 C/O logging and interpretation experiences in Indonesia since 1993. Job planning and well preparation critical to successful use of the technology are discussed. Several log examples are shown to highlight a cross section of applications in hopes of encouraging increased future use of the technology in optimizing reservoir performance.
Creative Interdisciplinary Team's Effort Results in Economic Development of a Previously Sub-Economic Field, South Zelda Field, Offshore Southeast Sumatra
Authors: Oglesby Chris A. , Schneider Mark , Pringgadani Meilando , Johnston Warren , Maulana Chandra , Williford John , Galuccio Miguel M. , Ridjab Timothy , Sambas Marlina
Published: December 2007

YPF/Maxus’ South Zelda field, offshore southeast Sumatra, Indonesia, was successfully developed in late 1998 with the installation of a braced caisson, the drilling of six development wells, and the successful tie-back and completion of the original discovery and delineation wells in the Zelda sandstones (Oligocene). At the platform’s October 1998 startup (prior to the development drilling and excluding the two non-platform wells), the field began producing at a rate of 2,500 BOPD from two wells and subsequent to the development drilling and completion of the remaining six platform wells in March 1999, the field’s anticipated production rate is over 8,000 BOPD. What made this project unique was the creative combination of engineering and science that converted a ten-year old sub-commercial discovery into an economic development despite the lowest oil prices since the field's discovery and without government incentives.

The South Zelda project was developed for $18MM as implemented, compared to $35MM estimated for a conventional development in the 1997 Plan of Development (POD). Savings resulted from innovative solutions implemented by the structural, drilling, and production engineering teams and the reservoir geology/engineering group. Using a caisson structure versus the traditional 4-pile platform resulted in savings of $5.4MM for platform and facilities. Tubular costs were lowered by $1MM by opting for smaller casing (7") and tubing (2-7/8") previously not used by the company in this area. And finally, a reservoir description project determined that the bulk of the reserves in the POD were in the Upper Zelda sandstones while the Middle and Lower Zelda reservoirs were riskier and poorer performers. Subsequently, YPF/Maxus chose to fully develop the Upper Zelda sandstones and to forego development of the deeper reservoirs, resulting in a decrease (from 12 to 10) in the required number of wells for full development. The ten wells include two development wells that were drilled from an existing platform to the north (Zelda C-14 and C-15), allowing YPF/Maxus to capture 100% of the Upper Zelda reserves in the 1997 POD.