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

主要研究白云岩的性质、白云化过程及其对白云岩储层空间分布的影响。白云化通常被认为发生在具有高水岩比的开放成岩系统中，在这种系统中，有效的流体流动将Mg引入系统，并允许形成大量白云岩，这在地质记录中得到了证明。以往的白云化研究几乎完全集中在开放成岩体系中的白云化。***我们的初步调查已经确定了Bakken储层中不同数量的白云岩。这些致密的非常规储层中白云岩的出现与我们通常认为白云化发生在开放成岩体系中的假设相矛盾。尽管非常规油藏生产了大量的油气，但对这些白云岩的岩石学和地球化学还没有系统的研究，它们的性质和起源仍然是推测性的。因此，来自非常规Bakken储层的白云岩为揭示相对封闭的成岩系统中白云岩的性质提供了独特的机会。***拟系统研究萨斯喀彻温省东南部非常规Bakken储层白云岩的岩石学、空间分布、成岩共生作用及地球化学特征。研究结果将有助于进一步认识相对封闭的成岩系统中白云岩的性质和控制白云化的因素，有助于进一步认识不同成岩环境下白云岩的成因和白云化时间。在过去的15年里，我对萨斯喀彻温省东南部常规储层的白云岩进行了研究，在那里我成功地应用了岩石学和地球化学的综合方法来研究不同地层的白云岩，这项研究是我之前工作的自然进展。***由于水平井多级水力压裂技术的成功应用，Bakken组是目前萨斯喀彻温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，从而可以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储层长期储存二氧化碳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.**