The origin and characteristics of dolomite from unconventional Bakken reservoirs in southeast Saskatchewan

本课题的研究重点是白云岩的性质、白云岩化过程及其对白云岩储层空间分布的影响。白云石化通常被认为发生在具有高水/岩比的开放成岩系统中，其中有效的流体流动将Mg输入系统中，并允许形成大量的白云岩，如地质记录所示。以往的成岩作用研究主要集中在开放成岩体系中的成岩作用。 * 我们的初步调查已经确定巴肯水库中的白云石数量不一。这些致密非常规储层中白云岩的出现与我们关于白云石化发生在开放成岩系统中的一般假设相矛盾。尽管大量的石油/天然气生产的非常规巴肯储层，一直没有系统的研究，这些岩石的岩相学和地球化学和他们的性质和起源仍然是猜测。因此，来自非常规巴肯储层的白云岩提供了一个独特的机会，可以在一个相对封闭的成岩系统中揭示白云岩的性质。* 拟议的研究计划系统地研究萨斯喀彻温省东南部非常规巴肯储层中识别出的方解石的岩相学、空间分布、成岩共生和地球化学特征。研究结果将有助于更好地了解白云岩的性质和相对封闭的成岩系统中白云石化的控制因素，从而加深我们对白云岩成因和不同成岩环境下白云石化时间的认识。拟议的研究是我以前的工作在过去的15年中，在萨斯喀彻温省东南部的常规水库，在那里我成功地应用了综合岩相学和地球化学方法来研究白云石从不同的地层白云石的自然进展。* 由于多级水力压裂技术在水平威尔斯井中的成功应用，Bakken地层目前是萨斯喀彻温省东南部非常规石油资源最热门的勘探目标。更好地记录Bakken储层中的白云岩及其寄主岩石岩性，有助于更好地了解这些非常规储层的地质力学特性，这些特性可用于优化水力压裂压力，以最大限度地提高石油产量。从拟议的研究中获得的岩性信息也将为巴肯水库内长期储存CO2的风险评估提供重要数据。

My research focuses on studying the nature of dolomite and processes of dolomitization and their implications for spatial distribution of dolomite reservoirs. Dolomitization is commonly assumed to occur in open diagenetic systems with high water/rock ratios where effective fluid flow imports Mg into the system and allows for the formation of the massive amount of dolomite as evidenced in the geologic record. Previous research on dolomitization has almost exclusively focused on dolomitization in open diagenetic systems. ***Our preliminary investigations have identified variable amounts of dolomite in Bakken reservoirs. Occurrences of dolomite in these tight, unconventional reservoirs contradict our general assumption that dolomitization occurs in an open diagenetic system. Despite the large amounts of oil/gas produced from unconventional Bakken reservoirs, there has been no systematic study concerning the petrography and geochemistry of these dolomites and their nature and origin remain speculative. As a result, dolomite from the unconventional Bakken reservoirs provides a unique opportunity to unravel the nature of dolomite in a relatively closed diagenetic system. ***The proposed research plans to systematically study the petrography, spatial distribution, diagenetic paragenesis, and geochemical signature of the dolomites identified from the unconventional Bakken reservoirs in SE Saskatchewan. Results of this study will provide a better understanding of the nature of dolomite and factors that control dolomitization in relatively closed diagenetic systems, which will advance our general knowledge about the origin of dolomite and the timing of dolomitization in different diagenetic settings. The proposed research is a natural progression of my previous work over the last 15 years on dolomite from conventional reservoirs in SE Saskatchewan, where I have successfully applied an integrated petrographical and geochemical approach to study dolomite from different strata. ***The Bakken Formation is currently the hottest exploration target for unconventional oil resources in SE Saskatchewan thanks to the successful application of multi-stage hydraulic fracturing technology to horizontal wells. Better documentation of dolomite and its host rock litholology in Bakken reservoirs could contribute to a better understanding of the geomechanical properties of these unconventional reservoirs, which can be used for optimization of hydraulic fracture pressure to maximize oil production. Lithological information derived from the proposed research will also provide important data for risk assessment of the long-term storage of CO2 within Bakken reservoirs.**