Title Preparing a Fractured Carbonate Field for Steam Injection
Author B. Wassing, SPE, J. van Wunnik, SPE, G. Warrlich, A. Lamki, SPE, T. Johnson, J. Gittins, SPE, and M. Riyami, SPE, Petroleum Development Oman LLC
SPE 118792-MS 2008 96.96% Relevance
The subject field is a fractured carbonate reservoir located in the Ghaba Salt Basin in Oman containing heavy, viscous oil. The field was discovered in 1972 and has been producing since 1976 through a process of mainly fracture depletion and natural water-influx. Without the application of an EOR technique the recovery will be low as the processes that displace oil from the matrix reservoir rock are adversely affected by the rock and fluid properties, particularly the high oil viscosity. Following the success of the steam-assisted GOGD test in an analogous nearby field, the field is being screened for feasibility of this thermal recovery process. In the steam-assisted GOGD process the fracture network plays a dual role : as distribution system of crestally injected steam to heat up the oil in the matrix and as offtake point deeper down in the column where the oil collects in the fracture oil-rim, after having drained predominantly through the matrix. Critical data on the fracture network and thermal PVT properties are collected and integrated in dynamic models to assess the oil drainage rate under steam injection. In modeling the SA-GOGD process, care needs to be taken to correctly represent the effect of unevenly heated matrix blocks on the oil viscosity and hence drainage rates. Oil close to the steam filled fractures will heat up more quickly than in the center of the matrix blocks and the former will start to drain faster than the latter.
阿曼的Ghaba Salt盆地的一个裂缝型碳酸盐稠油油藏。1972年油田被发现，随着1976生产，裂缝中的油枯竭，地层水入侵。 由于没有采取EOR技术补救措施,，采收率非常低。油藏基质岩石和其中驱体出的原油，其岩石和流体性质，特别是原油的粘度,都受到了严重伤害。附近一个类似的油田，筛选使用热力提高采收率的可行性，随后用蒸汽协助GOGD测试，得到成功。在蒸汽协助GOGD过程，裂缝网格扮演一个双重角色：一边顶部注入蒸汽的分配体系加热基质中的油，一边在环柱中泄入到更低的地方，油在裂缝外缘汇集。在注入蒸汽之后，在动态模型中收集关于裂缝网络和热力PVT物性的重要数据来评估泄油能力 。在对SA-GOGD建模过程中，注意要正确地反应出基质岩石加热不均匀性对原油粘度和泄油速度的影响。而在充满蒸汽裂缝中的原油,比中心基质岩石的原油加热的速度要快,前者的泄油速度也比后者快.
Ignoring this effect and using viscosity values based on averaged temperatures and established viscosity-temperature relationship, as is usually done in dual permeability simulation, will underestimate the SA-GOGD drainage rates. This underestimation will increase with a larger difference between the cold and hot oil viscosity and is also more relevant to early times (economics). A new method has been developed to conserve the 1D-drainage rate of unevenly heated matrix blocks based on an effective or “pseudo” viscosity correlated with gridblock-averaged temperature.
Title Simultaneous Acid Diversion and Water Control in Carbonate Reservoirs: A Case History From Saudi Arabia
Author Ali A. Al-Taq, SPE, Hisham A. Nasr-El-Din, Jimmy K. Beresky, and Khalid M. Naimi, Saudi Aramco; and Leopoldo Sierra, SPE, and Larry Eoff, SPE, Halliburton
SPE 106951-PA 2008 96.96% Relevance
Journal SPE Reservoir Evaluation & Engineering
Volume Volume 11, Number 5
Date October 2008
Pages pp. 882-891
Copyright 2008. Society of Petroleum Engineers
Matrix acidizing and water control are usually addressed as two separate issues. Associative polymers can be used to simultaneously achieve effective acidizing and water control during a single treatment. A polymer-based treatment was applied in an offshore, perforated vertical well with two sets of perforations in a carbonate reservoir in Saudi Arabia. The acid treatment was needed to restore the productivity of the upper set of perforations and reduce water production from the lower set of perforations.
通常是将基质酸化和控水作为二个不同问题分别进行处理。 用单一手段处理作业期间，聚合物的运用就可以达到同时有效的酸化和控水的效果。 在近海沿岸运用了一种聚合物基进行处理作业，在沙特阿拉伯碳酸盐储层的直井中射二套孔眼， 酸处理是需要的恢复上部那套射孔孔眼的生产能力，下部那套射孔孔眼是为了减少出水量。
Experimental studies were carried out to investigate the potential use of associative polymers to control water mobility and act as an acid diverter. Coreflood experiments were conducted on reservoir cores at downhole conditions (temperature of 200°F and pressure of 3,500 psi). Extensive laboratory testing showed that associative polymers had no significant effect on the relative permeability to oil. However, the relative permeability to water was significantly reduced.
This paper presents a case history where an associative polymer was applied during matrix acid treatment of a damaged well. The treatment included two stages of associative polymer solutions and 20 wt% HCl with additives. Post-stimulation treatment production data showed that oil rate increased 11.18-fold, whereas water rate decreased 1.7-fold, resulting in a reduction in the water cut from 75 to 14 vol%.
The production logging tool (PLT) results indicated that the associative polymer was effective in diverting the acid into the oil producing zone. The upper set of perforations was producing most of the fluid, which further confirmed that the associative polymer significantly reduced water production from the lower zone.
Title Innovative Methods To Improve Carbonate Reservoirs Modeling Accuracy and Reliability
Author David Foulon, Total E&P Qatar; Louise den Boer, Total HQ France; Florence Vieban, Total E&P Qatar; and Rashed Noman, and Mohamed Labiadh, Qatar Petroleum
SPE 105203-MS 2007 96.96% Relevance
While they already contain around half of the world’s hydrocarbon reserves, carbonate fields still exhibit lower recovery factors than clastic fields. A major explanation lies in the more complex intrinsic structure and higher chemical reactivity of carbonate rocks. Because it is linked to both the depositional and the biological environment, the genetic pore network is more complicated than in classical sandstones. Moreover; it is usually strongly reworked after deposition by superimposed diagenetic processes as well as fracturing phases. This creates levels of heterogeneity orders of magnitude higher than in clastic environments. As a result, small scale heterogeneity is often a key driver of fluid flow in carbonates. Proper, reliable modeling of this critical heterogeneity remains a pitfall often preventing efficient reservoir simulation and development.
This paper recaps the traditional upscaling methods used for heterogeneity modeling, and highlights their limitations when applied to carbonates. It presents an innovative line of thinking to overcome these limitations, grounded on robust geological concepts and tied to core and log data. The corresponding reservoir modeling involves the dual porosity structure, not for fracture modeling, but for splitting the porous medium between the fluid portion mainly involved in pressure support and the one sweepable liable to be readily swept.
This innovative workflow, coupled to smart experimental designs matching techniques, was applied to a mature carbonate field in the Middle East. It enabled to reach a first-time successful history matching, and to highlight significant additional development potential. Conceptually simple and numerically efficient, this methodology could be extended to other highly heterogeneous fields.
Title Waterflood Conformance Study for a Carbonate Reservoir
Author Khalaf Al Anzi, Rajendra Kumar, Tahani Al Rashidi, Kuwait Oil Company, John Cumming, Howard McKean, Calum McKie, Halliburton
SPE 111363-MS 2007
Mature fields of the Middle East have some of the longest production histories and richest data sets of any oilfields in the world. Waterfloods in fields that have operated for many years are reaching a stage in which better understanding of the reservoir’s response to water injection is critical for optimal field management going forward.
A common approach, however, is that existing data sets are often used only by individual technical disciplines for relatively narrow purposes, such as well performance diagnoses.
An integrated, multidisciplinary study of a carbonate reservoir in the Minagish Field was implemented to better evaluate the conformance and integrity of current water injection operations, and make recommendations for improvement. A secondary objective was to establish a solid interdisciplinary workflow to support periodic reevaluation and update of the study.
A joint team of reservoir engineers and geoscientists was formed from KOC’s West Kuwait Asset Team and Halliburton’s Landmark group. Using a Common Visualization Environment (CVE) (Figure 1), the team integrated the Minagish Field history with all available static and dynamic data into a single, consistent data set.
KOC的西部科威特评估组和哈里伯顿兰德马克绘图国际公司联合油藏工程师和地球学家组成一个小组。 使用公用可视化环境(CVE) (图1)，把Minagish油田所有可利用的静态和动态历史数据集成为单一兼容的数据集。
A detailed geologic model with compartmentalization and layering schemes was established which was most likely to control fluid movements within the reservoir. This was validated and a more consistent model was developed by incorporating dynamic field data. The revised model based on flow units was further validated by cross-sectional reservoir simulation models in selected areas of the field.
This study suggests KOC can produce the Minagish Field at significantly higher offtakes in the future without negatively impacting recovery.
Title Fracturing Mechanism and Fracture Systems Analysis of Carbonate Reservoir from Abu Dhabi - UAE
Abu Dhabi – UAE的碳酸盐岩油藏的裂缝形成机制和裂缝体系分析
Author M. Sirat, SPE, Petroleum Institute, and S.M. Salman and S. Bellah, ZADCO
SPE 111397-MS 2007 96.96% Relevance
Many fractured carbonate reservoirs of Abu Dhabi have different structural styles and exhibit unpredicted behavior for development-production realizations. We have studied one of these reservoirs that comprise a domal structure with very gentle dipping flanks, and high fractures density. These fractures play an important role in controlling fluid flow and recovery.
In this study, we present a conceptual model that explains the fracturing mechanism; formation, development and reactivations of these fractures. It also provides answers to questions about the main factors that control fracture geometries and densities with respect to reservoir structure and rock typing. Based on the available data from 2D seismics and cores examination, fracture systems identification and classification were carried out. We have also discussed the relationships between these fracture systems with curvature, faults and shear zones.
We believe that fracturing mechanism is mainly controlled by reactivations of the pre-existing basement faults (structural grain), which have been reflected throughout the sedimentary cover as two main fractures systems each of which comprises three fracture sets: one extensional and two conjugate shear ones. It is evident that curvature of doming whether on the crest (convexity) or on the flanks (concavity) have no major effect on fracture densities. Instead, fracture densities increase in the vicinity of faults or shear zones. Fracture densities also increase in dolomitic layers compared to limestones and anhydrates.
This new fracturing concept has a significant impact on production and recovery, where different scenarios for fractures opening/ reactivations due to the present state of stresses are presented.
Keywords: Fractured Carbonate reservoirs; fracturing mechanism; fracture systems; Abu Dhabi; UAE
Title Investigation of Water-Coning Phenomenon in Iranian Carbonate Fractured Reservoirs
Author M. Namani and M. Asadollahi, NIOC RIPI, and M. Haghighi, University of Tehran
SPE 108254-MS 2007 96.96% Relevance
The water coning caused by the imbalance between gravity and viscous forces is the most important reason for water production in different fractured reservoirs. There are various controllable and uncontrollable parameters affecting this phenomenon. In this study different dynamic models were constructed to search for the key parameters affecting the coning process in both single-well and Cartesian multi-well models.
It has been determined that oil layer thickness, perforation thickness, fracture permeability and its orientation, especially horizontal not vertical fracture permeability, production rate, mobility ratio, and fracture storativity have the major role in water coning phenomenon. Also it has been determined that fracture spacing, aquifer strength and skin factor have insignificant effect on water coning in fractured reservoirs. The variation of water breakthrough time respect to each effective parameter has also been studied. We concluded that for any production program or adjusting the wells location, the parameter study is very important.
Multi-well studies using an Iranian fractured reservoir data show that the trend of dependency of water coning on each parameter is similar to the single-well model. However, in field scale, it is necessary to have all reservoir data including well location, and production history for a successful water coning simulation because a small pressure drawdown exerted by a far well will affect the cone shape and its breakthrough time.
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