固体沥青对储层物性、孔隙结构及测井响应的定量评价

Solid bitumen has been found widely in the reservoir, which is polymer hydrocarbon compound that can not flow because of its high viscosity (also known as “dead oil”). The extent of reduction in porosity and permeability of the rock as a result of precipitation of the reservoir bitumen can be as destructive as the damage caused by interstitial material. Solid bitumen change the pore structure and strengthen the reservoir heterogeneity，and even influence hydrocarbon accumulation and productivity. It can form the bitumen sealed belt together with rock lithology, then form the lithologic reservoir which is not controlled by structure. Conventional logging response characteristics of bitumen are similar to that of oil and gas, such as interval transit time and resistivity. The solid bitumen which is difficult to develop is easily interpreted as oil and gas in well logging, which increase the difficulty of hydrocarbon reservoir recognition and optimization of perforation layer.The project intend to use bituminous reservoir derived from Cambrian Longwangmiao formation in Sichuan Basin and Jurassic and Triassic in Junggar Basin as the research object, through the comparison of the characteristics of sample before and after Hot solvent extraction by an organic solvent, including the observation under the microscope, porosity, permeability, nuclear magnetism, interval transit time and resistivity, which can quantitative evaluate the influence of solid bitumen on different types of reservoir property, pore throat structure and well logging parameters, in order to provide a theoretical basis for bituminous reservoir evaluation, hydrocarbon reservoir recognition, optimization of perforation layer, the establishment of reservoir geological model, calculation of hydrocarbon reserves, economic evaluation of reservoir and exploration of subtle reservoir.

固体沥青广泛存在于油气储集层中，因其粘度大，是不流动的高分子烃类化合物(又称“死油”),类似于充填在储层孔隙及喉道中的填隙物，可堵塞孔隙及喉道，降低储层的孔渗性能,改变储层的孔喉结构，使储层的非均质性增强,并可与岩性一道形成沥青封堵带，形成不受构造控制的岩性油气藏。沥青的声波时差和电阻率等测井响应特征与油气相似，这种难以开发并占据大量储集空间的固体沥青在测井上易被解释为油气，增大了油气层识别以及射孔层段优选的难度。项目拟以四川盆地寒武系龙王庙组、准噶尔盆地侏罗系和三叠系含沥青储层为研究对象，通过沥青溶解前后样品的镜下观察和孔隙度、渗透率、核磁共振、声波时差以及电阻率等特征分析，定量评价固体沥青对不同类型储层物性、孔隙结构以及测井参数的影响，为含沥青储层的评价、油气层识别、射孔层段的优选、油气藏地质模型的建立、油气储量计算、油气藏经济评价以及隐蔽性油气藏的勘探提供理论依据。

储层中的固体沥青类似充填在储层孔隙或裂缝中的胶结物和粘土矿物，占据储层的孔隙和喉道，不仅降低了储层孔隙度和渗透率，还改变后期油气的运移和聚集。固体沥青属于高密度不可流动的碳氢化合物，常规测井曲线上表现为高电阻率，沥青的测井识别一直都是困扰油田行业的难题，如何准确的识别沥青层对储层测井物性解释、油气地质储量计算和生产计划等各个方面均有重要影响。. 该基金以新疆三台-北三台地区侏罗系-三叠系储层沥青和四川磨溪地区龙王庙组焦沥青为主要研究对象，通过沥青溶解实验，对含沥青样品溶解前后的孔隙度、渗透率及孔隙结构等做了物性对比分析，定量评价固体沥青对储层物性的影响。同时，对含沥青样品溶解前后的声波时差、电阻率及核磁共振等测井参数进行对比分析，定量分析了沥青含量与电阻率、声波时差参数和核磁共振参数的相关性，并建立了核磁共振解释模型。最后，通过岩心实验分析结果，结合常规测井和核磁共振测井实例分析，建立了固体沥青的测井识别标准和识别方法。. 大量溶解实验分析：不同比例的二硫化碳+N-甲基-2-吡咯烷酮+氯仿+苯、二硫化碳+N.N-二甲基甲酰胺+N-甲基-2-吡咯烷酮+氯仿+苯的混合溶剂对焦沥青溶解效果最好。焦沥青的核磁共振响应非常弱，岩石总孔隙度大于核磁共振孔隙度，建立了核磁共振-岩石总孔隙度沥青解释模型。低成熟度沥青在核磁共振上具有非常强的响应，主要表现在T2时间0.01~4ms之间，含氢指数（HIapp）约为0.5。实例分析表明，低成熟度沥青和重质稠油在核磁共振测井上T2弛豫时间短，T1LM/T2LM值随流体粘度的变化而变化，密度孔隙度与校正后的核磁共振孔隙度存在较大的差值，因此结合核磁共振解释模型和常规测井参数，可对低成熟度沥青或稠油层进行有效的识别。