Integrating XRD and Well Logging Data to Establish Electro-Facies and Permeability Models for an Unconventional Heterogeneous Tight Gas Reservoir, Obaiyed Giant Gas Field

I. Mabrouk
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Abstract

Formation evaluation in heterogeneous reservoirs can be very challenging especially in fields that extend over several kilometers in area where the permeability varies from 0.1 mD up to 1000 D within the same porosity. The porosity, hydrocarbon saturation and net sand thickness in most of Obaiyed field wells are consistent; hence, the productivity of these wells is enormously dependent on the reservoir permeability. Since the permeability is highly heterogeneous, initial production rate of the wells varies between few MMSCFD to almost one hundred MMSCFD. The huge permeability variation led to a tremendous uncertainty in the dynamic modeling, which resulted in an inaccurate production forecast affecting the field economics estimation. Understanding permeability distribution and heterogeneity in Obaiyed field is the key factor for establishing a realistic permeability model, which will lead to a successful field development strategy. Extensive work was performed to understand key factors that govern the permeability in Obaiyed using the data of 1-kilometer length of cores acquired in more than 50 wells covering different reservoir properties in the field. Core data were used to separate the reservoir into different Hydraulic Flow Units (HFU) according to Amaefule's work performed on the Kozeny-Carmen model. Afterwards, a correlation between the HFU and well logs was established using IPSOM Electro-Facies module in order to define the flow units in un-cored wells. The result of this correlation was used to calibrate a Porosity-Permeability relationship for each flow unit. The next step was examining the clay-type distribution and diagenesis in each flow unit using the petrographic analysis (XRD) results from the core xdata. All factors controlling the permeability can now be represented in hydraulic flow units which are considered as a method of measurement of the reservoir quality. Consequently, property maps were constructed showing the location and continuity of each of the flow units, leading to a more deterministic approach in the well placement process. Based on this new work methodology, a production cut-off criteria relating the reservoir productivity to both clay minerals presence and percentages was established for multiple wells scenarios. As a result, the development strategy of the field changed from only vertical wells to include horizontal wells as well which proved to be the only economic approach to produce the Illite dominated zones. This paper presents a workflow to provide a representative estimation of permeability in extremely heterogeneous reservoirs especially the ones dominated by complex clay distribution.
结合XRD和测井数据建立非常规非均质致密气藏电相及渗透率模型
非均质储层的储层评价是非常具有挑战性的,特别是在渗透率从0.1 mD到1000 D不等,延伸数公里的油田。大部分油田井的孔隙度、含油饱和度和净砂厚度基本一致;因此,这些井的产能很大程度上取决于储层渗透率。由于渗透率是高度非均匀的,因此井的初始产量在几MMSCFD到近100 MMSCFD之间变化。巨大的渗透率变化导致动态建模存在很大的不确定性,导致产量预测不准确,影响油田经济效益评价。了解目标油田的渗透率分布和非均质性是建立符合实际的渗透率模型的关键因素,这将有助于制定成功的油田开发策略。为了了解影响Obaiyed渗透率的关键因素,研究人员进行了大量工作,使用了50多口井1公里长的岩心数据,覆盖了油田不同的储层性质。根据Amaefule在Kozeny-Carmen模型上所做的工作,利用岩心数据将储层划分为不同的水力流量单元(HFU)。随后,使用IPSOM电相模块建立HFU与测井曲线之间的相关性,以确定未取心井的流动单元。这种相关性的结果被用来校准每个流动单元的孔隙度-渗透率关系。下一步是使用岩心xdata的岩石学分析(XRD)结果检查每个流动单元中的粘土类型分布和成岩作用。控制渗透率的所有因素现在都可以用水力流量单位表示,水力流量单位被认为是测量储层质量的一种方法。因此,构建了属性图,显示了每个流动单元的位置和连续性,从而在排井过程中提供了更确定的方法。基于这种新的工作方法,建立了一个将储层产能与粘土矿物存在和百分比联系起来的生产截止标准,适用于多口井。因此,该油田的开发策略从只开发直井转变为同时开发水平井,这被证明是开采伊利石占主导地位的唯一经济途径。本文提出了一种具有代表性的非均质储层渗透率估算方法,特别是以复杂粘土分布为主的储层渗透率估算方法。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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