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Keys to Success in Determination of In-Situ Petrophysical Properties of Unconsolidated Sands by Traced-Coring: A Case Study

机译:Traced-Coring测定未覆盖的原位岩石物理性质的成功键:案例研究

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Objectives of obtaining in-situ values of water saturation, formation water salinity, true formation resistivity (Rt) and SCAL data by core analysis can only be achieved if extraneous fluid invasion is kept at a controlled level and corrected for it or be prevented. The impossibility of zero invasion of cores by mud-filtrate makes the traced-coring a compelling method. Application of liquid based tracers such as tritium and deuterium oxide (D20) to determine the amount of fluid invasion is highly recommended in the event of critical in-situ formation properties need to be determined from core. This study presents a set of key factors for controlling invasion of core by extraneous fluids, best practices in quantifying the fluid invasion, handling core at the surface, and suggests types of analyses, specifically, for unconsolidated formations. A comparison of petrophysical parameters determined from traced-core against the results of LWD log interpretation of the same interval is also presented to assess the success/failure of the recommended practices. The main use of core-driven parameters has dual functionalities. They are used for calibrating LWD data and also are used to form a statistical database for static modeling. Calibration of LWD data with properly obtained core parameters could minimize uncertainties in calculated petrophysical parameters and establish a ground-truth in petrophysical work especially in water saturation (Sw) calculations. In our case study, good agreements are observed between log derived and core measured water saturations and salinity values extracted from the core against salinity from petrophysical study. Proper time management, core preservation technique, prompt logistical arrangements and well-site core plugging are seen as the main driving factors for a successful coring job. Comparison of fluid invasion profiles between core plugs drilled at well-site and plugs drilled later in the lab are presented to demonstrate and emphasize the importance of time-factor which constitutes the main challenge in the case study and in general. The lack of data from uncontaminated core may result in significant financial losses that may manifest itself as bypassed productive zones, erroneously determined as wet or no-production (dry) intervals, wrong completions or incorrect quantification of actual and recoverable hydrocarbons. Some of these problems are associated with lack or mismanagement of uncertainties in calculation procedures/ algorithms; therefore, can be alleviated or lessened with representative and accurate core data. In addition, analyses results based on the representative core could promote better understanding of reservoir behavior and catalyze more refined reservoir management strategy. The experience acquired in this study revealed and ranked the importance of timing of the events and the procedural steps to obtain minimally invaded core plugs in a traced-core operation. Time is the most critical factor to prevent post-drill fluid-invasion and fluid re-distribution within a core which adversely impact core analysis results. Therefore, the optimum time allowed between the coring and laboratory tests, core transportation strategy, corresponding contamination of core as a function of time, recommended tests, selection of tracers and quick calculation of required tracer volume are the outputs that are elaborated in this paper. This study also highlights potential challenges in coring unconsolidated formations and serves a mitigation plan for lessening invasion of core by providing a set of recommendations for best practices.
机译:如果在受控水平处保持外来流体侵袭并校正或防止,则只能实现获得核心饱和度,形成水盐度,真实地层电阻率(RT)和SCAS数据的原位值的目标。通过泥滤液零侵入核心的不可能性使追踪冠的诱惑方法。在临界原位形成特性的情况下,强烈推荐使用液体基于氧化物和氘氧化物(D20)的施用液体的示踪剂以确定流体侵袭的量需要从核心确定。本研究提出了一系列用于通过外来流体控制核心的侵袭,定量流体侵袭,表面处理核心的最佳实践的一组关键因素,以及表明分析类型,具体地用于未溶解的地层。还提出了对来自追踪核心的岩石物理参数对同一间隔的LWD Log解释结果的比较,以评估推荐措施的成功/失败。核心驱动参数的主要使用具有双重功能。它们用于校准LWD数据,并且还用于形成静态建模的统计数据库。具有适当获得的核心参数的LWD数据的校准可以最大限度地减少计算出的岩石物理参数中的不确定性,并在岩石物理工作中建立普通的实际实际,尤其是水饱和度(SW)计算。在我们的案例研究中,在从岩石物理学研究中从核心提取的日志衍生和核心测量的水饱和饱和饱和饱和饱和饱和饱和饱和饱和饱和度和盐度值之间观察到良好的协议。适当的时间管理,核心保存技术,促销后勤安排和良好的网站核心堵漏被视为成功取芯作业的主要驱动因素。提出了在实验室后钻井的钻井和塞钻的芯塞之间的流体侵入型材的比较,以证明并强调时间因素的重要性,这在案例研究中构成了主要挑战。未污染核心的缺乏数据可能会导致显着的财务损失,可能表现为旁路生产区域,错误地确定为湿或无生产(干)间隔,错误的完井或实际碳氢化合物的量化不正确。其中一些问题与计算程序/算法中的不确定因素缺乏或不确定相关;因此,可以用代表性和准确的核心数据来缓解或减少。此外,根据代表性核心的分析结果可以促进对水库行为的更好理解,并催化更精细的水库管理策略。本研究中获得的经验揭示并排名了事件时序的重要性和在追踪核心操作中获得最小侵入的核心插头的程序步骤的重要性。时间是防止钻孔后液体侵入和流体重新分布的最关键因素,这在不利地影响核心分析结果。因此,芯片与实验室测试之间允许的最佳时间,核心运输策略,作为时间的函数的核心污染,推荐的测试,追踪器的选择以及所需的示踪体积的快速计算是本文阐述的输出。本研究还突出了无核分子未结核地层中的潜在挑战,并为通过提供一套建议进行最佳实践来减少核心入侵的缓解计划。

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