深层含沥青溶孔-溶洞型碳酸盐岩微观导电特性

Microconductivity of deep， bitumen-bearing carbonate rocks of dissolved pore and cavity types： A case study of the Cambrian Longwangmiao Formation in the Gaoshiti-Moxi area， Sichuan Basin

吴丰 梁芸 唐松 李昱翰 田兴旺 杨辉廷 李锋

Feng WU Yun LIANG Song TANG Yuhan LI Xingwang TIAN Huiting YANG Feng LI

沥青广泛存在于深层碳酸盐岩储集空间中，沥青不仅严重影响储层物性与含气性，还导致储层测井电阻率响应复杂，增加了含沥青碳酸盐岩储层有效性评价、流体性质判别与含水饱和度计算的难度。以四川盆地安岳气田高石梯—磨溪地区寒武系龙王庙组含沥青溶孔-溶洞型碳酸盐岩为研究对象，开展微米CT扫描数据分析研究，采用数字岩心技术对储层孔隙结构和沥青充填特征进行表征，建立不同沥青含量和不同含水饱和度条件下的三维岩石导电模型，利用有限元方法开展岩石导电数值模拟，研究了沥青对碳酸盐岩导电特性的影响机理。研究结果表明：①含沥青溶洞型与溶孔型碳酸盐岩电阻率值与沥青含量呈正相关、与含水饱和度呈负相关。②溶孔型碳酸盐岩的狭窄喉道更易被沥青堵塞，使其导电性受沥青的影响较溶洞型碳酸盐岩更大。③低含水饱和度状态下，地层水主要以束缚水膜的形式赋存于储集空间表面，沥青使束缚水膜变得不完整，导致溶洞型和溶孔型碳酸盐岩电阻率急剧增大。④相比含沥青溶洞型碳酸盐岩，含沥青溶孔型碳酸盐岩具有更大的胶结指数（）和更小的饱和度指数（）。

Bitumen， which is widely found in the storage spaces of deep carbonate reservoirs， significantly affects the physical and gas-bearing properties of the reservoirs and complicates their resistivity logging responses. This makes it more difficult to evaluate the effectiveness of bitumen-bearing carbonate reservoirs， determine fluid properties， and calculate water saturation. This study focuses on the bitumen-bearing carbonate rocks of dissolved pore and cavity types in the Cambrian Longwangmiao Formation in the Gaoshiti-Moxi area， Anyue gas field， Sichuan Basin. Based on the analysis of the micro-CT scanning data， we characterize the pore structures and bitumen-filling characteristics of the carbonate reservoirs using digital core modeling. As a result， 3D rock conductivity models with varying bitumen content and water saturation conditions are established. Then， numerical simulations of rock conductivity are conducted using the finite element method， and the mechanisms through which bitumen influences the conductivity of carbonate rocks are investigated. The results indicate that the resistivities of bitumen-bearing carbonate rocks of both types exhibit a positive correlation with the bitumen content and a negative correlation with water saturation. Since the narrow throats in dissolved pore-type carbonate rocks are more prone to be blocked by bitumen， the conductivity of these rocks is more subjected to bitumen effect than the dissolved cavity-type carbonate rocks. Under low water saturation， formation water mainly occurs as irreducible water films on storage space surfaces. However， these water films become incomplete in the presence of bitumen， leading to a sharp increase in resistivity for both types of carbonate rocks. Compared to bitumen-bearing dissolved cavity-type carbonate rocks， the dissolved pore-type reservoirs exhibit a higher cementation exponent （） and a lower saturation exponent （）.

10.11743/ogg20250120