bluuebunny/crossref_metadata_2025 huggingface dataset:
Accurate, Efficient Quantification of Uncertainty for Flow in Heterogeneous Reservoirs Using the KLME Approach
Authors: Lu Z. , Zhang D.
Published: December 2007

Accurate modeling of flow in oil/gas reservoirs requires a detailed description of reservoir properties such as permeability and porosity. However, such reservoirs are inherently heterogeneous and exhibit a high degree of spatial variability in medium properties. Significant spatial heterogeneity and a limited number of measurements lead to uncertainty in characterization of reservoir properties and thus, to uncertainty in predicting flow in the reservoirs. As a result, the equations that govern flow in such reservoirs are treated as stochastic partial differential equations. The current industrial practice is to tackle the problem of uncertainty quantification by Monte Carlo simulations (MCS). This entails generating a large number of equally likely random realizations of the reservoir fields with parameter statistics derived from sampling, solving deterministic flow equations for each realization, and post-processing the results over all realizations to obtain sample moments of the solution. This approach has the advantages of applying to a broad range of both linear and nonlinear flow problems, but has a number of potential drawbacks. To properly resolve high frequency space-time fluctuations in random parameters, it is necessary to employ fine numerical grids in space-time. Therefore, the computation effort for each realization is usually large, especially for large-scale reservoirs. As a result, a detailed assessment of the uncertainty associated with flow performance predictions is rarely performed.

In this work, we develop an accurate yet efficient approach for solving flow problems in heterogeneous reservoirs. We do so by obtaining higher-order solutions of the prediction and the associated uncertainty of reservoir flow quantities using the moment-equation approach based on Karhunen-Loéve decomposition (KLME). The KLME approach is developed on the basis of the Karhunen-Loéve (KL) decomposition, polynomial expansion, and perturbation methods. We conduct Monte Carlo simulations and compare MCS results against different orders of approximations from the KLME method. The three-dimensional computational examples demonstrate that this KLME method is computationally more efficient than both Monte Carlo simulations and the conventional moment-equation method. The KLME approach allows us to evaluate higher-order terms that are needed for the highly heterogeneous reservoirs. In addition, just like the Monte Carlo method the KLME approach can be implemented with existing simulators in a straightforward manner and are inherently parallel. The efficiency of the KLME method makes it possible to simulate fluid flow in large-scale heterogeneous reservoirs.
Integrated Visualization and manipulation of well data for maximizing data value and delivering well-informed decisions for a shallow Tar Formation
Authors: Zubari H. , Murty CRK , Ramamoorthy R. , Srivatsava A. , Stowe I.
Published: December 2007

The Aruma zone in the Bahrain field is a shallow dolomitic limestone with vugs filled with heavy oil and tar. Due to difficult fluid and rock properties, the reservoir was deemed unproductive and the zone was routinely cased off to reach deeper productive horizons.

Bapco has recently launched a project to investigate the producibility of the zone under advanced IOR techniques and lifting technology. A fluid and rock data acquisition program was initiated to characterize the reservoir, which included advanced logs and core acquisition. Wellbore instability made both log and core acquisition challenging. This paper discusses the experience with the rock characterization using advanced integration software.

Due to the large volume of data acquired from a variety of advanced logs and core, it was a challenge to efficiently and effectively integrate all data and ensure utilization of every piece of information. In this paper, we demonstrate the importance and value added by using a system that facilitates integration, manipulation and simultaneous wellbore visualization in 2D and 3D Canvasses in an interactive environment. We illustrate the positive impact of such visualization on data quality assessment in zones of borehole induced artifacts.

We demonstrate the several interactions that serve to add value to the acquired information. We also discuss the impact that such visualization and interaction capability has on the accuracy of decisions made on the well and on the validity of the characterization of the reservoir rock in the near wellbore region
Integration of Dynamic & Geostatic Data Improves Reservoir Characterization
Authors: Al-Henshiri M. Y. , Arisaka K. , Al-Hassani H. , Al-Yasi T. , Fujita N.
Published: December 2007

Integration of the dynamic data and geologic data led to a significant enhancement in understanding the reservoir flow behavior of a major limestone reservoir in the Arabian Gulf. High-permeability streaks were found to be the main factor controlling the reservoir performance and water breakthrough in the northern sector of the field.

The methodology presented in this paper integrates static and dynamic data in such a way to ensure consistency between the data and enable better understanding of the reservoir flow characteristics. The study accommodates all available data from core, well test, O.H. logs, PLT, PNC logs and production data.

Core data was used to identify the permeability variations vertically and horizontally. In order to extend the knowledge and map the area where the high-perm streaks exist, well test, production logs, TDT/PDK logs, production and injection data were used to link the reservoir heterogeneity on well-well and on a field scale basis. Statistical wire line log analysis was conducted and found that the Rxo log response was quite useful for reservoir characterization in this regard. The results of the analysis showed good consistency with what was concluded from dynamic data.

The core and dynamic data indicate the high-permeability streaks cannot be correlated all over the reservoir, they are strictly present in the northern sector. There is a clear borderline splitting the reservoir into two sectors, the high permeability northern sector, and the low permeability southern sector.

The profiles measured with the production logs (WFL & TDT/PDK) consistently indicated the presence preferential behavior that interpreted as a high–permeability streaks at the top part of the reservoir. A linear increasing WOR trend of the wet producers is a clear indication of presence of permeability contrast that interpreted as a presence of hi-permeability streaks. The dual-permeability/porosity behavior as interpreted analytically utilizing pressure transient data found to be the response of the presence of hi-permeability streaks.

This paper shows how data integration improved our understanding of reservoir performance and reduced the production uncertainty of this heterogeneous limestone reservoir. The modified 3D simulation model matched, for the first time, the reservoir water cut performance.
The Role of Strike-Slip Faulting on Deep ‘Basement’ Faults in Cretaceous Depositional History and Fiqa Channel Location, as Determined from Analysis of 3D Seismic Over an Offshore Field, Abu Dhabi
Authors: Edwards E. , Al-Rougha H. B. , Sit H. , Sultan A. , Khouri N.
Published: December 2007

From structural analysis of 3D seismic data over a giant field, offshore Abu Dhabi, a complex pattern of intersecting, broadly conjugate, strike-slip dominated en-echelon fault systems are observed from ‘basement’ levels up to latest Cretaceous horizons. Over geologic time these fault systems exerted fundamental controls on depositional patterns within the study area. Use of new attribute techniques, isochron mapping, flattening on key intra-Cretaceous horizons, cinematic time-slice ‘movies’ and a review of the available vertical seismic sections has indicated that many apparent velocity anomaly zones are controlled by deep-seated fault systems developed as strike-slip dominated ‘flower structures’. Spatial continuity of these fault zones, the most prominent of which trend ~NE-SW, exhibit a linear nature on a scale of several kilometers to tens of kilometers; have flower-zone geometry in cross-section but with increasingly en-echelon nature at Upper Cretaceous levels; low apparent normal offsets on long fault segments; anastomosing, convergent and divergent, patterns at different stratigraphic levels; wrench offset with respect to other deep fault systems; throw terminations with rapidly decreasing displacement gradients along en-echelon zones into the crossover zones with other fault systems. There are four prominent fault systems that exert control on the depositional systems: (1) NE to NNE trending ‘Fiqa’ direction, also delineating local depositional highs/lows and Mishrif ‘reef’ margin; (2) NW-SE zones defining depositional areas of step-wise thickening/thinning; (3) Conjugate WNW-ESE and WSW-ENE en-echelon strike-slip zones, and (4) NNW-SSE fault zones displaying local control on thinning or thickening. Temporal fault activity on these zones is linked to sedimentary thickening and thinning patterns, though deeper level faults provided only ‘soft’ links to the sedimentary sequences of early Cretaceous age. By late Cretaceous times the transtensional / transpressional fault systems provided ‘hard’ links to the deposition systems (e.g. Fiqa channel system).
Optimisation of Stimulation Techniques for HP, Deep Wells in the Harweel Cluster, Oman
Authors: Laws M. S. , Al-Riyami A. M. N. , Soek H. F. , Abdulkadir R.
Published: December 2007

This paper describes the strategy that was developed to optimise acid stimulation of the Harweel Cluster Phase 1 wells. Initial treatments involved bullheading 15% gelled HCl. The latter treatments involved spotting 15% HCl and Emulsified Acid with coiled tubing using a Dynamic Diversion Technique. The results of the various methods were carefully assessed during subsequent well tests. Inflow profiles before and after stimulation have been successfully adapted by the application of the Dynamic Diversion technique. In addition, the Emulsified Acid system has also shown superior diversion characteristics compared to gelled 15% HCl. All of the key learnings from these initial stimulations are presented together with a recommended way forward.
Resistivity Anisotropy and its Impact on Reserves Estimates and Technology Applications in North Kuwait Reservoirs
Authors: Azim S. A. , Abdullah S. M. , Al-Zaabi H. , Al-Awadi W. , Najeh H. M. , Bryant W. B. , Aldred R. , Steel M.
Published: December 2007

Laminated shaly sand sequences are often overlooked when determining pay intervals in clastic reservoirs. This is because traditional methods of calculating hydrocarbon saturations in these formations use resistivity measurements and one of the numerous shaly-sand saturation equations. These techniques generally understimate the hydrocarbon content because conventional resistivity measurements are dominated by the conductive component of the formation, in this case shale. Even when the excess conductivity due to the shale is accurately accounted for in the calculation, there is still a high degree of uncertainty in the results.

Laminated sequences such as these are commonly found in the Burgan Formation in the Raudhatain and Sabiriyah Fields in North Kuwait. They have traditionally been considered as non-pay and the hydrocarbon content of marginally shaly formations has generally been underestimated.

Recent work re-evaluating wireline log measurements in these fields, taking the shaly formations into account, has significantly increased the volume of hydrocarbons in place. However, there remained a high degree of uncertainty in the results. These new estimates can now be confirmed, and the uncertainty removed, by the combined use of vertical and horizontal resistivity measurements. The measurements, made using a multi-component induction logging tool, measure the electrical anisotropy of the formation, and as such can give a greatly improved measure of the conductivity of the thin sand layers within the laminated sequences. Additionally, these measurements can be used to determine whether the shaly sand is a laterally extensive laminated formation or a disturbed non-reservoir quality rock.

This paper will review the technology used to acquire the measurements, show examples from the wells logged in North Kuwait, and describe the impact on reserves estimates. The paper also highlights a successful case of active interaction between KOC Field Development and Research & Technology Groups and Baker Atlas as a service company.
A New Wireless Solution to Real Time Reservoir Surveillance
Authors: Brinsden M.
Published: December 2007

The transmission of wellbore parameters from near the sandface has traditionally been achieved using a data transmission cable containing a shielded conductor or an optical fibre bundle. The cable is installed as part of the well completion and requires wellhead and packer penetrations. There have been numerous attempts to achieve effective data transmission from the sandface to surface utilizing either the well tubulars or the formation as an acoustic or electromagnetic transmission media, without repeaters. Achieving this type of wireless telemetry has been a goal of many equipment suppliers. Trials of a new electromagnetic system for transmitting data without cables have now shown that it is indeed possible to obtain data without wires. This revolutionary technology opens up two quite contrasting opportunities to operators, firstly in obtaining data from near the sandface in both existing and new wells without permanent monitoring systems and secondly, in providing wireless flow control at the sandface. This paper specifically reviews the data transmission capabilities of the system with the help of two case studies, which demonstrate the application of wireless telemetry data acquisition in retrofit and permanently installed applications.
New Oil in an Old Reservoir: Prize from a Comprehensive, Multi-Disciplinary Reservoir Management Approach in Sabiriyah Lower Burgan Reservoir in North Kuwait
Authors: Al-Ajmi M. F. , Chetri H. B. , Khan A. N. , Al-Anzi E.
Published: December 2007

Prior 2001, the overall potential as well as the viability of the long-term development of the Lower Burgan Sandstone reservoir in Sabiriyah field (SA LB) in North Kuwait were somewhat uncertain. This was mainly due to two factors; wet crude handling limited capacity (given that over 70% of the producers were wet) and the fact that the reservoir produced about 65% of its reserves. Additional penetrations into this mature reservoir out side its 1998 foot print (through deepening other reservoirs' new wells to SA LB), have resulted in extending SA LB reservoir both areally and vertically indicating new development frontiers and promising a significantly increased reservoir potential.

At that time, a multi-disciplinary team was formed to evaluate the reservoir. Better understanding of the reservoir geology, rock and fluid description, and well's performance provided the frame to make effective changes in terms of management as well as development options of this high oil API/naturally pressure supported reservoir.

The well-integrated SA LB team (four to five members) comprises petroleum engineers, geologists, and reservoir engineers, with petrophysical and geophysical support. The great efficiency of the teamwork method was combined with an excellent atmosphere of communication and collaboration with the operational and service company's personnel. The new teamworking environment has yielded significant benefit in resource and technology utilization.

The previous organization approach often compromised SA LB production/potential through focusing on the other water flooded reservoirs and treated it as a swing producer. It suffered from the absence of a proper definition of the reservoir before commitment of non-representive development plan as a swing producer with no infill opportunities.

This paper demonstrates and emphasizes the importance of developing an accurate reservoir description, realistic/flexible development plan, and comprehensive management through the joint efforts of the geologists and engineers.
Water Flooding a Heterogeneous Clastic Upper Burgan Reservoir in North Kuwait: Tackling the Reservoir Management & Injectivity Challenges
Authors: Chetri H. B. , Sturrock D. , Al-Roweyah A. , Al-Dashti H. , Al-Mufarej M. , Clark R.
Published: December 2007

bstract

Multi-layered Upper Burgan reservoir in Sabiriyah Field of North Kuwait began production in the 1950's and is currently undergoing an accelerated phase of Water flood development.Historical Oil production from the reservoir has resulted in the decline of reservoir pressure on the crest of the structure to a level close to the bubble point. In order to augment to the reservoir energy, an injection scheme was attempted utilizing an inverted nine-spot pattern at the crest of the structure in 2000, utilizing the same grid pattern as in the overlying super giant mauddud reservoir, by dueling the injectors & producers. Later on, seeing the actual water injection performance and water flood response, it was discovered that an optimistic view of the sand continuity and the injectivity in high permeability clastics was adopted in the past, while finalizing the water flood strategy.

The severe heterogeneity and compartmentalization of the Upper Burgan reservoir coupled with formation damage, poor injection water quality & poor injectivity have slowed down the pace of the water flood development of the reservoir. It is becoming apparent that in order to implement water flood in the Upper Burgan, a scheme must be developed which takes into account the complex reservoir geometry and the practical problems of injecting variable quality water into a clastic reservoir.

Several well intervention techniques, more vigilant monitoring of the injection water quality and proppant frac jobs at the injectors yielded little improvement, far below the target injection rates. Eventually, multitude of Step rate tests was conducted to find options, leading to the decision of injecting above the formation parting pressure.

A detailed geological mapping is underway, followed by a full field static/ dynamic modeling. The current depletion strategy is focused at producing the segments with reservoir pressures higher than 3000 psia and choking back the wells at the depleted crestal part. The ongoing drilling plan has also been suitably tailored to target the segments with higher level of reservoir pressures for well placement. This reservoir management strategy has led to an increase in production by about 60%, as compared to the level about 2 years back.

The case history to be presented in the paper highlights how the production growth is being achieved in a NK reservoir beating the impact of delayed water flood.
Successful Application of Production Optimization Models to Sustain Field Target and to Defer Capital Investment in Offshore Khafji Field
Authors: Ghoniem E. O. , Samizo N. , Al-Thuwainy A.
Published: December 2007

Khafji field, lies in the Arabian Gulf 40 km offshore east of Al-Khafji, Saudi Arabia, commenced production in 1961, and is currently producing with average rate of over 300MBOPD.

The artificial lift, by limited capacity of 25 MMSCF/D of lift gas, was introduced in 1988 which could successfully sustain field target.Although the additional artificial lift energy was required to sustain the target rate, production optimization was found one of the solutions to prolong to sustain the target, which could result in deferring a huge capital investment.

The paper describes the construction and use of general optimization and allocation models for Khafji field which simulates the combined performance of the reservoirs, wells and surfaces gathering network.

Individual well models and surface gathering network have been built from the mid of perforations to separators at GOSPs.The more accurate multiphase flow correlation has been selected to generate performance curves.These models were calibrated and validated against actual field data with (−1.2%) average percentage error, (2.5%) average absolute percentage error and (3.5%) standard deviation, then lift gas was automatically re-distributed between wells.

A marginal gain of approximately 12,000 BOPD was concluded by lift gas optimization, and an additional gain of 15,000 BOPD can be obtained by flowline de-bottlenecking with some additions and revisions of flowline network to reduce wellhead back pressure.

Finally, these models are useful tool for production optimization to sustain field target also for routine production operations taking into account the field and system constraints, furthermore prediction of future system requirements.
Permeability Anisotropy Measurement on Whole Cores—Analytical Solution and Application
Authors: Al-Yousef H. Y.
Published: December 2007

This paper presents an analytical solution for the steady-state flow problem for the anisotropic permeability measurement. It also describes a practical procedure that implements the solution to evaluate permeability anisotropy. The procedure requires a few steady-state measurements of flow rates and pressure drops at different directions from which the maximum and minimum permeability values and their directions can be determined. The application of the new solution and the proposed method is demonstrated by measurements on whole core samples. Comparison between results obtained using the new solution for the anisotropic case and the existing solution for the isotropic case is discussed.
Reservoir Screening and Sensitivity Analysis of Waterflooding With Smart Wells Through the Application of Experimental Design
Authors: Esmaiel T. E. H. , Fallah S. , van Kruijsdijk C. P. J. W.
Published: December 2007

This study demonstrates the feasibility of creating a response surface proxy model, using experimental design and analysis, to facilitate Monte Carlo simulation, uncertainty analysis and screening of performance forecasts. In particular we applied the technique to assess the value of smart wells in waterflooding a heterogeneous reservoir and to examine the sensitivity to geologic, production and economic parameters. This was achieved through the generation of proxy models using various d-optimal designs with a full factorial design for comparison. The models were further validated with independent simulations to verify the predictions.

The computationally efficient proxy models allowed Monte Carlo analysis to determine sensitivities and the quantification of an increase in expected value through the use of smart wells. The improvements in simulation speed were in the order of 1,000 to 10,000 times faster. In the examples studied we found that the negative impact of geological features on the waterflooding performance could be almost entirely mitigated through dynamic flow control with smart wells operating under rate constraints.This provided an options value due to reduced risk in addition to an increase in the expected NPV.The Monte Carlo analysis also allowed the quantification of the value of information in collecting additional data to reduce the uncertainty in reservoir properties and the resulting reduction in NPV uncertainty.
Analysis Behind Casing: A Window for Improved Reservoir Management of a Mature Bahrain Oil Field
Authors: Murty C. R. K. , Zubari H. , Srivatsava A. , Ramamoorthy R. , Rampurwala M. A.
Published: December 2007

Management of mature oil fields requires accurate formation evaluation information. The ability to acquire essential data through casing adds a new dimension to reservoir characterization and affects the reservoir development of a mature oilfield like the Bahrain field. New logging tools and technology fill the gap in evaluation, especially for monitoring water saturation changes over time and for detecting bypassed oil pockets across the zone.

In this paper we present the results and validity of a logging through casing run in a depleted well completed in a sandstone reservoir in the Bahrain oilfield. The reservoir has a complex lithology of high-permeability sandstone with thin interbeds of siltstone and shale, erratically deposited but prolific in oil production. The objectives of the data acquisition were to monitor oil depletion through casing and to study the effect of lithology on the water encroachment pattern across the zone.

In this paper we describe the interpretation procedures and data validation of the information obtained from an advanced suite of logs run through casing. The paper also focuses on how this new information has resulted in a review of potential further development of this pay in one part of the field.
Investigation of Thermal Gas-Oil Gravity Drainage (GOGD) in Fractured Carbonate Reservoirs
Authors: Ayatolahi S. , Boukadi F. , Wadhahi M. , Maamari R. , Bemani A.
Published: December 2007

In Oman, it is known that the oil content in matrix porosity in fractured carbonate oil reservoirs exceeds more than 90% of the oil originally in place. Minimal recovery factors during the primary stages of production are due to the nature of these carbonate reservoirs; geometry and extent of the fracture network, matrix permeability, wettability tendency, as well as the nature of the fluid system. The occurrence of a strong water drive, in some of the fields, becomes even more detrimental to primary recovery.

The Omani oilfield of Qarn Alam, with a naturally-fractured Shuaiba carbonate reservoir, is at the center of this investigation. Its reservoir contains 213 million cubic meters of heavy crude (16 oAPI and 220 cp) with an expected ultimate oil recovery of 2% of STOIIP, under primary depletion. Intensive theoretical and experimental studies are carried out in an attempt to quantify potential gains from the Gas-oil Gravity Drainage (GOGD) mechanism that is taking place in the reservoir. Investigations will be undertaken to validate the theory that the combined effects of matrix accessibility to the trapped oil by hot gas, oil viscosity reduction, and the possible oil bank formation are contributing to a higher oil recovery factor during GOGD.
Using Gradients to Refine Parameterisation in Field-Case History Match Projects
Authors: Cominelli A. , Ferdinandi F. , De Montleau P. C. , Rossi R.
Published: December 2007

Reservoir management is based on the prediction of reservoir performance by means of numerical simulation models. Reliable predictions require that the numerical model mimics the known production history of the field. Then, the numerical model is iteratively modified to match the production data with the simulation. This process is termed history matching (HM).

Mathematically, history matching can be seen as an optimisation problem where the target is to minimize an objective function quantifying the misfit between observed and simulated production data. One of the main problems in history matching is the choice of an effective parameterization: a set of reservoir properties that can be plausibly altered to get an history matched model. This issue is known as parameter identification problem and its solution usually represents a significant step toward the achievement of an history matched model

In this paper we propose a practical implementation of a multi-scale approach to identify effective parameterizations in reallife HM problems. The approach is based on the availability of gradient simulators, capable of providing the user with derivatives of the objective function with respect to the parameters at hand. Those derivatives can then be used in a multi-scale setting to define a sequence of richer and richer parameterisations. At each step of the sequence the matching of the production data is improved. The methodology validated on synthetic case and has been applied to history match the simulation model of a North-Sea oil reservoir.

The proposed methodology can be considered a practical solution for parameter identification problems in many real cases. This until sound methodologies, primarily adaptive multi scale estimation of parameters, will become available in commercial software programs.
Wettability Index Determination by Nuclear Magnetic Resonance
Authors: Looyestijn W. , Hofman J.
Published: December 2007

Knowing the wetting condition of a reservoir at an early stage is crucial for selecting optimum field development options. Paying insufficient attention to the wetting condition e.g. assuming water wet behavior) may result in incorrect STOIIP estimates, and in unexpected dynamic behavior, e.g. under water flooding.

A novel method is presented to determine the in-situ wettability of rocks from NMR logs. The method is based on the fact that fluids experience additional relaxation when in direct contact with the rock surface. A reduction of the oil relaxation time away from its bulk value is generally known as a qualitative wettability indicator. Through detailed modeling of the NMR response, this concept has been further developed to provide a quantitative wettability index. It is based on a model for the microscopic distribution of the crude oil and the wetting state of the rock at any given overall saturation. The method requires an NMR measurement on a sample containing two reservoir fluids, i.e. brine and crude oil. Multi-acquisition schemes including diffusion effects make the interpretation more robust, but a normal NMR acquisition suffices and can be made with all available NMR tools (wireline and LWD).

The new NMR based method has been extensively verified on core data against standard wettability tests. Application to NMR logs from several fields, and in particular carbonates, show continuous profiles of varying wettability, ranging from fairly oil-wet, through intermediate, to waterwet, all in line with the available core data.
Operating Experience With Dual and Triple Slimhole Injectors in Coalinga
Authors: Zahedi A. , Johnson R.
Published: December 2007

The Coalinga field is one of the oldest oilfields in California and has been under production for over 100 years. The Temblor sands comprise the major reservoir in Coalinga at a depth of 500-2200 ft, with porosity of 33%, oil gravity of 12-14 API, and air permeability of 0.7-3 darcies. Each Temblor sand is at a different stage of drainage and thermal maturity requiring different steam injection rates in each zone.

A significant number of slimhole injectors have been drilled in Coalinga dedicated to single zones as a way to control steam injection in multiple-zone steamflooding. Nearly 200 slimhole injectors were drilled at Coalinga from 1988 to 2002.

Dual and triple string slimhole injector designs were used in West Coalinga as a cheaper alternative for conventional dual and triple zone injector completions. However, operating problems with some of the slimhole wells have negated much of the cost savings.

Currently all triple slimhole injectors are shut-in as most of them have experienced near surface tubing failures and subsequent steam migration to the surface. Some of the dual and triple slimhole injectors drilled in close proximity to each other at Coalinga have experienced steam migration out of the perforated zones into nearby zones due to low quality cement placement in the triple completions.

Monitoring and operation of the triple injectors has been a difficult task due to their surface equipment design. This has shown that operational and monitoring design related issues need to be addressed in detail prior to field implementation. This paper discusses the performance history of slimhole design injection wells in Coalinga. It reviews advantages and disadvantages of dual and triple slimhole injectors, compares single and multiple string slimhole injectors with similar conventional injectors, and shows general field examples of historical slimhole operational and monitoring issues.
Better Results Using Integrated Production Models for Gas Wells
Authors: Harms L. K.
Published: December 2007

While each engineering discipline may have a piece of the puzzle to find the best solution for achieving optimized production rates and economics, we can only hope to achieve the best results if we use a total system (reservoir to sales point) approach. Relatively simple to use software tools are available to help and can be easily applied, especially on gas wells. However, effective use of these tools will require the engineering disciplines to break down silos, possibly compromise on using their "favorite" tools and work together. Examples and case histories on gas wells are shown to demonstrate how each discipline looks at solving problems and how better solutions are found using an integrated production model (IPM).
An Experimental Investigation of Reaction-Transport Phenomena During Co2 Injection
Authors: Egermann P. , Bazin B. , Vizika O.
Published: December 2007

The injection of carbon dioxide in depleted petroleum reservoirs or in aquifers is a promising way to cope with the short-medium term issue of greenhouse gas emissions mitigation. Several coupled physical and chemical processes may occur during the injection depending on time and location within the reservoir. Far field regions are facing long term reaction in a situation where flow of gas and water at a reduced rate may induce near fluid-rock equilibrium. In contrast, near well-bore regions are subjected mainly to gas at a high flow rate where dissolution/reprecipitation phenomena may increase/decrease drastically the injectivity.

The purpose of this study is to investigate experimentally the various situations in representative reservoir conditions with the objective of achieving knowledge and data for future physical and numerical modeling and reservoir numerical simulations of CO2 re-injection. Experiments consist in the co-injection of CO2 and brine in carbonate cores (limestone). The temperature and pressure conditions are such that the CO2 is in supercritical state. Results show that the flow rate and the composition of the fluids initially present in the core play a major role in the fluid-rock interaction leading to various non-uniform dissolution facies and in some cases to re-precipitation and permeability reduction. These phenomena have been observed and quantified using various non destructive techniques (NMR, CT-scanner) and chemical analyses of the producing fluids, leading to a comprehensive understanding of the coupled mechanisms taking place.
Career Development System; A Giant Nascent
Authors: AbouHeif M.
Published: December 2007

A pioneer local attempt presenting new experiences and valuable contribution to the oil and gas industry careers and competences development.

Businesses used to partner with employees to carry out employees’ career planning and development. Times have changed. Now, businesses are coming to view career development primarily as the employee's responsibility. However, proper guidelines, procedures and systems are furnished and huge resources are made available by the businesses to help employees in their career planning and provide managers with the right judgment tools.

Such resources and capabilities are usually not available to the national and local companies. Tailoring a precision "Career Development System" to suite the local environments and compete, at the same time, with the multinationals' capabilities is not an easy task.

The Career Development System: Tells employees where they stand;Shows employees their possible career paths;Helps employees to choose the career path that best matches their competences, ambitions and vision;Describes a detailed step by step procedure to develop competences and to move up the ladder from one position to the other in each career path;Supplies the necessary follow-up sheets and forms to help each manager and employee in taking timely & correct career decisions and, at the same time, guarantees the fairness and the proper implementation of each procedure.

Our company's "Career Development System" has passed through many stages starting from the "need rise" stage, the "system building" stage, the "validation & revision" stage, the "implementation" stage, up to the "evaluation" stage.

This paper goes through all these different stages, describing the difficulties of each stage, suggesting solutionsbased on our gained experience and offering some picked examples from our system. As a conclusion, this paper also describes the positive impact of this system on all our business aspects.

We wish to present our experience to all national and local companies in our area to help setting the example and simply say that WE DID IT.
Integration Tools to Streamline Reservoir Management and Field Development Workflows for Mature Fields in South Oman
Authors: Naguib M. A. , Shahin E. , Moore J.
Published: December 2007

Enhancements in software, hardware, expertise, data collection and interpretation have continued to improve the industry's ability to build detailed 3D geologic and dynamic flow models of the subsurface and to take rational reservoir development decisions. There continues, however, to be much skepticism about the ability of the same process to contribute to day to day reservoir management and optimization of mature assets.

This paper describes how a truly integrated approach can shorten the planning and study timeframe and reduce uncertainty for reservoir management in such mature assets. Also presented is a system which links on-line (real-time and near real-time) downhole, surface and corporate data to ensure that reservoir, well and facilities models are constantly updated to reflect actual operating conditions. Using this "always current" encapsulation of the production system (between reservoir and delivery point) we perform a wide range of tasks to manage the asset performance: surveillance activity planning, production optimization, facilities optimization and debottlenecking, production forecasting and allocation.

The system integrates a number of existing software applications, and reduces the number of complex engineering tasks. It is being applied in a number of operational environments and the results of some are presented: Workflow and examples for integrating dynamic simulation output with static model and production data.Tool for waterflood pattern analysis and integration with well and production historyLive visualization of SCADA/DCS data via PI system and integration with reservoir understanding to provide a tool for accelerated identification of optimization potential

This integration process has a very positive impact on reducing the processing time for each task, and the visualization formats assist communication within the multidisciplinary reservoir management team. Embedding these tools in the reservoir management and field development process aids decision making and accelerates production thereby increasing the value of these mature fields.
Water-Free, Drill-In Fluid Dramatically Improved the Producibility of Sensitive Sandstone Reservoirs
Authors: Al-Ammari S. M. , Phillips J. E. , Ogunsola A. , Al-Mumen A. A. , Ezzat A. M.
Published: December 2007

New water-free, oil-based drill-in and completion fluids were recently utilized to drill a sensitive sandstone reservoir.Lower fluid densities were required to safely stabilize the wellbore compared to water-based fluids previously used in the offset wells.Avoiding excessive overbalance pressures eliminated differential sticking, minimized hole enlargement, and significantly reduced formation damage.Upon reaching the target horizontal depth, clean treated oil was circulated to remove the wallcake and solids-free viscosified oil was used as the completion fluid.Two horizontal wells were successfully drilled and completed with pre-pack and expandable screens. Quick clean up was achieved without stimulation.Sustained production rates of these wells exceeded expectations and improved productivity indexes were achieved.

The systems used were chemically non-reactive with the rock minerals and reservoir fluids and were less invasive to preserve the native state of the rock along with its natural wettability. Based on the reservoir rock morphology and the calculated pore throat size distribution, the bridging particles type, size distribution, and concentration were selected to rapidly establish a tight thin wallcake and prevent the invasion of fine drilled solids deep into the formation.

Comparative laboratory data was generated using natural core samples and different types of fluids.Some of these fluids reduced clay hydration and swelling, but failed to totally prevent dislodging and mobilization of fines.Authegenic clays were present as pore filling fine particles in some cores.Destabilizing these fines and forcing them to move choked off the interconnections between the pores as clearly shown in the thin sections studies.

This paper discusses the reservoir rock sensitivity data, the drill-in fluid formulation and its formation protection characteristics, and the field applications and production data.Also presented are the recommended guidelines for designing and monitoring the quality of this type of drill-in and completion fluids in the field.
Tipping Point Leadership, Discipline Quality Experts and Quality Assurance in ADCO
Authors: Gyllensten A.
Published: December 2007

"Tipping-point leadership" is a modern management approach designed to overcome resistance to change and improve performance. In ADCO the introduction of Discipline Quality Experts builds on the idea that in any organization there are people, procedures and systems that has a disproportionate impact on performance - like hitting the kingpin in bowling brings down all the other pins!

This is particularly important in Petroleum Development, the core of modern Oil & Gas companies. Although highly technical such organizations are now often "Asset focused" and as a result functional skills may suffer. This causes dilemmas for a learning organization, which is also trying to grow significant numbers of young national staff and integrate them in their midst. In ADCO Discipline Quality Experts in key disciplines like Geoscience, Petrophysics, Reservoir- and Petroleum- Engineering are located in a Quality and Performance Improvement Department (QPID) charged with conducting gap analyses on a continuous basis to monitor critical business areas and suggest new opportunities for change to maximize the value of existing assets. Peer Reviews, Discipline Forums and Balanced Scorecards are utilized to monitor individual and team performance contracts and monthly Project Boards review the business value of major projects and studies.

The Discipline Quality Experts provide Asset teams with expert advice and consultation in areas that directly impact short and long term activities. They conduct quarterly reviews to ensure that Field Development Plans meet the business targets and are in line with Shareholders’ guidelines. They play a key role in the introduction of minimum standards for competency assurance and foster a challenging and motivating learning environment for all staff. They also lead the discipline coordination meetings to ensure the transfer of "Best Practices" across Asset teams.

This paper will illustrate the approach taken in applying these principles to the Petrophysics Discipline in the Petroleum Development Division (PDD) in ADCO.
Mechanics of Borehole Ballooning in Naturally-Fractured Formations
Authors: Lavrov A. , Tronvoll J.
Published: December 2007

The mechanics of borehole ballooning caused by opening / closing of a single fracture intersected during drilling in a naturally-fractured reservoir is explained by means of a coupled analytical model. Equations governing borehole ballooning are summarized for different types of fluid rheology. The effects of various parameters on the fluid flow during a ballooning event are analyzed numerically. Shortcomings of the developed modeling approach are outlined.
A Case Study on Redevelopment of a Giant Highly Fractured Carbonate Reservoir in Iran Based on Integrated Reservoir Characterization and 3D Modeling Studies
Authors: de Galard J. -H. , Zoormand G. H. , Ghanizadeh M. , Daltaban S. , Camus D.
Published: December 2007

This field is located within the Zagros fold belt in the South West Iran and is producing in highly fractured carbonate Asmari and Bangestan reservoirs.

It's a 70 km long anticline with about 50 billions barrels of initial oil in place and a small initial gas cap; initial oil column is 2000 m of 32 API crude with properties varying with depth. The field was discovered in 1937 and produced by natural depletion until 1977 when gas injection was initiated in the gas cap.

A total of 320 wells were drilled on the structure.

A full field reservoir study was conducted to propose a new Master Development Plan to maximize hydrocarbon recovery.

This paper presents:

The reservoir characterization mainly based on rock typing and its extension to uncored wells, on fracture characterization and modeling study and on the construction of a full field geostatistical fine grid model.

The reservoir simulations including phenomenological studies on sector models to determine the proper PVT model to use in the full field model and to quantify impact of fracture properties, matrix bloc sizes, diffusion, block to block interaction on reservoir performance and a full field simulation model with dual porosity media and improved black oil options.

Combination of drive mechanisms acting in this field such as gas gravity drainage, diffusion and convection were represented.

Various redevelopment options studied indicate that the overall oil recovery can be improved by gas injection pattern improvement and selected infill drilling with proper completion strategy.
Eliminating Multiple Interventions Using a Single Rig-Up Coiled-Tubing Solution
Authors: Kumar P. S. , Gisbergen S. V. , Harris J. , Ferdiansyah E. , Brady M. , Harthy S. A. , Pandey A.
Published: December 2007

This paper describes new methods to economically improve production levels in one of the mature fields of Petroleum Development Oman. This field had been developed by infill drilling programs, which were suspended in early 2001 to review the development strategy. A reservoir management team set a challenge to effectively conduct logging operations and quickly utilize the data collected to identify and avail of optimization opportunities, thus maximizing the production of the wells whilst lowering overall costs. The optimization activity consisted of clean-out, saturation logging, perforation and stimulation. These activities were carried out either with coiled tubing only utilizing conventional practises and e-line coiled tubing, or with the combination of coiled tubing and hoist through multiple well entries. Both of these methods were successfull in that they resulted in incremental net oil production but at relatively high costs.

This paper presents a methodology which enables clean-out, logging, stimulation and perforation with one coiled tubing intervention, which includes a plastic coated "e-line" coiled tubing, coiled tubing perforating head and new perforation technology. All systems are in complete compliance with the most stringent safety criteria. The new method has a considerable time and cost savings impact, and this is fully illustrated in this paper with field trial case histories, in which a multi-disciplinary team effectively targeted the most suitable zones for perforation and stimulation using a state of the art self diverting, non damaging, acid system. Technical and economic comparisons are made with conventional practices. The methodology is currently being employed in this field and is potentially applicable to other fields.