页岩油、气甜点构成要素比较研究

The hydrocarbon accumulates in shale appears significant mechanism differing from the conventional, a cluster of factors favorably combined at a right geologic zone leads to form a beneficial hydrocarbon accumulation - 'Sweet Spot', due to its reservation in oneself and displacement versus strand. Therefore, of much importance for shale hydrocarbon appraisal and production is to finger out the occurrence of the sweet spot. It is proposed, by this application proposal, the major elements of geologic factors for sweet spot forming may be demonstrated by analyzing the mechanism and the qualification of hydrocarbon's enrichment in shale, that commence on the study on the composition of essential materials that subjects to shale hydrocarbon, solids including inorganic rocks / minerals and organic kerogen, fluids including oil and gas, and the mechanism that solid and fluid affected with each other (displacement / strand, adsorption / disadsorption), and by the study of the space (pore, fracture) in shale available for the deposition and the phases (adsorption, free and dissolution) of hydrocarbon, and then, to clarify the trade-off among some factors and to differ the requirements of shale attributers for oil to gas. Sequentially, The dominant elements of sweet spot of shale oil and gas may be comprehensively concluded by optimization and objective function of management, through forward modeling based on known wells and inverse modeling of well to seismic data based on geologic setting and petrophysics, and error analysis as a consequence by comparing to dynamic producing data.

页岩油气与常规油气的富集机理大不相同，因其自生自储特征和排替/滞留规律，一组地质要素在合适部位的有机组合形成页岩油气富集的有利目标-"甜点"。因此，确定"甜点"的分布对于准确评价和经济开发页岩油气有着极其重要的作用。本申请研究项目提出，从构成页岩油气的基本物质-固体（无机的岩石和有机的干酪根）、流体（油和气）及其它们之间的相互作用机理（排替与滞留、吸附与解吸附）的出发，通过对页岩储集空间（孔隙、裂缝）及油气赋存方式（吸附、游离、溶解）的研究，分析页岩油气的富集机理及富集条件，阐述"甜点"构成的地质要件和主控因素，厘清相关参数的此消彼长关系，比较分析油和气的储层特征需求差异，确定页岩油气"甜点"的构成要素。形式上是通过已知油气藏解剖的正演模拟和基于地质背景研究及岩石物理分析的井震资料联合反演，基于最优化技术和目标函数管理来对页岩油气甜点构成要素综合评判，最后，结合动态数据分析进行误差分析。

页岩油气已成为我国重要的油气替补资源，但与常规油气的富集机理大不相同的是其具有自生自储的特征和排替/滞留规律，经济有效的开发是要找到页岩地层中油气富集的“甜点”。本项研究从构成页岩油气的基本物质-固体（无机的岩石和有机的干酪根）、流体（油和气）及其它们之间的相互作用机理出发，通过对页岩储集空间及油气赋存方式的研究，分析了页岩油和气的富集机理及富集条件及其差异性，阐述了“甜点”构成的地质要件和主控因素，厘清了相关地质参数的此消彼长关系，确定了页岩油气“甜点”的构成要素，构建了要素组织图。.研究指出页岩油和气的主要储集空间和赋存方式存有差异：页岩气的主要储集空间为有机质孔隙，裂缝更多的是起到渗流的作用；页岩油的有机质孔隙较为不发育，其储集空间主要为无机孔隙（包括裂缝）。其赋存方式页岩气以吸附态为主，页岩油以游离态为主。长宁区块下志留统龙马溪组页岩气的储集空间主要有黏土孔隙和有机质孔隙，济阳坳陷沙河街组的页岩油的储集空间以黏土孔隙和裂隙为主。页岩中油气的富集是其本身的滞留，它受控于有机质的丰度和类型、热演化程度、储存条件、岩相、温度、压力和油气物性等因素。泥页岩地层滞留油的能力远远大于滞留气的能力，泥页岩储层对富集条件的控制主要为有利的矿物组合和有机质热演化过程中普遍发育的地层超压。.页岩油气藏“甜点”构成要素具有共性，主要由生烃能力、储油气条件及易开采性三个方面来决定。前两项属“地质甜点”范畴，后者属“工程甜点”范畴。优质生烃条件包括沉积时位于盆地沉降中心，烃源岩厚度大、有机质丰度高、类型好，经过了适宜生油气窗的演化阶段。良好储集条件包括具有良好保存条件的自生自储式成藏模式、内部天然裂缝发育、不间断供气和连续聚集。“工程甜点”主要由页岩的矿物组成来决定，如四川盆地长宁地区龙马溪组优质页岩的脆性矿物含量能达到60%以上，济阳坳陷沾化凹陷罗家地区沙三下亚段页岩脆性指数达到了50%以上。