深层、超深层致密碳酸盐岩储层固态沥青测井评价——以川中地区上震旦统灯四段为例

Logging Evaluation of Solid Bitumen in Tight Carbonate in Deepburied and Ultra-deep-buried Strata of the Central Sichuan Basin

超深、超老地层中的非常规油气成藏及演化、甜点区刻画、资源潜力定量评价是非常规油气沉积学的一大难点,相关定量评价技术和理论的发展对推进我国“两深一非”油气勘探具有现实意义。沥青是古油藏存在的直接证据,对探索古油藏分布、规模、成藏机制及论证研究区油气勘探潜力具有重要理论和实践意义。以川中地区上震旦统灯影组灯四段为研究对象,先综合岩芯观察、铸体薄片镜下观察、图像法定量计算,对固态沥青进行了表征;而后建立了多矿物体积模型,借助常规测井曲线组合(DEN-RT-RXO-CNL-AC),对储层固态沥青进行反演,克服了储层固态沥青分布的强非均质性,定量评价了灯四段固态沥青的含量及分布。研究结果表明:1)灯四段沥青多以半充填状态存在于孔隙中,储层固态沥青含量可达4.62%,平均为2.20%;纵向上,灯四上亚段固态沥青含量普遍高于灯四下亚段;2)高石梯—磨溪地区与德阳—安岳裂陷槽紧邻的台缘礁滩体是古油藏聚集的有利区域,储层固态沥青含量普遍高于东侧的含气区;3)受自西向东油气充注控制,高石梯—磨溪地区南北向固态沥青含量无明显差异。古隆起北斜坡灯四段固态沥青的存在证实了北斜坡古油藏的存在,从侧面印证了北斜坡的油气成藏潜力。从固态沥青的角度,坚定了继续深化川中古隆起北斜坡深层、超深层油气勘探的必要性。

The accumulation and evolution of unconventional oil and gas,locating sweet spots and quantitative evaluation of resource potential in ultradeep,ultraold strata are the major difficulties in unconventional petroleum sedimentology.The development of relevant quantitative evaluation techniques and theories is of practical significance to promote"two deep and one unconventional"petroleum exploration policy in China.Solid bitumen is direct evidence of the existence of paleo-reservoirs,which is of great theoretical and practical significance to explore the distribution,scale and petroleum accumulation mechanism of paleo-reservoirs,and to demonstrate the exploration potential of oil and gas in the study area.In this paper,the fourth member of the Dengying Formation of Upper Sinian in Central Sichuan was taken as the research object.Firstly,the solid bitumen was characterized by core observation,microscopic observation in thin section and image processing method.Then,a multi-mineral volumetric model was established,and the inversion of the solid bitumen was carried out with the aid of the conventional logging curve combination(DEN-RT-RXO-CNL-AC),which overcame the substantial heterogeneity of the distribution of solid bitumen and quantitatively evaluated the content and distribution of the solid bitumen in the fourth member of the Dengying Formation.The results show that:(1)Most of the Dengsi member bitumens exist in the pores in a half-filled state,and the solid content of the reservoir can reach 4.62%,with an average value of 2.20%;vertically,the content of the solid bitumen in the upper subsection of the fourth member of Dengying Formation is generally higher than that in the lower subsection.(2)The reef-flat facies in the platform margin of Gaoshiti-Moxi area,which closed to the Deyang-Anyue rift trough,are the desirable areas for the formation of paleo-oil-reservoirs.The content of solid bitumen in reef-flat facies is generally higher than that in the eastern gas-bearing area.(3)There is no significant difference in the content of solid bitumen in the north-south direction due to oil charging from west to East.The existence of solid bitumen in the fourth member of Dengying formation in the north slope of the paleo-uplift confirms the existence of the paleo oil reservoir in the north slope and also confirms the oil and gas resources potential of the north slope from the side.From the point of view of solid bitumen,it is necessary to continue to deepen the deep and ultra-deep oil and gas exploration in the north slope of the Central Sichuan Paleo-Uplift.