有效储层物性下限和产能约束下深层碎屑岩储层多参数分类评价方法

Multi-parameter classification and evaluation methods of clastic reservoir under the constraint of effective reservoir physical property lower limit and productivity

合理的储层分类评价方法对深层碎屑岩储层的油气勘探具有重要的意义。以东营凹陷古近系深层碎屑岩储层为研究对象,总结了一套适合于深层碎屑岩储层的"有效储层物性下限和产能约束下碎屑岩储层多参数分类评价方法",即在储层特征和有效储层物性下限研究的基础上,以孔隙度差值和渗透率差值为对比评价参数,分析有效储层发育的主控因素,通过不同控制因素的耦合对储层进行综合分类,以单井经济产能为约束,评价不同类型储层的经济潜力,并采用多种图件叠合的方法预测有效储层分布规律。研究表明,东营凹陷古近系沙河街组深层主要发育湖底扇、近岸水下扇和洪水—漫湖等储集砂体,发育常压、弱超压、中超压及强超压4种压力系统,主要处在中成岩A_1亚期、中成岩A_2亚期和中成岩B期。在控制有效储层发育的各因素中,沉积作用是最重要的控制因素,成岩作用受控于沉积作用和地层压力。综合考虑有效储层的控制因素,将东营凹陷古近系沙河街组深部储层划分为4类8亚类,以单井经济产能为约束的评价表明,其中Ⅰ类、Ⅱ_1亚类及部分Ⅱ_2亚类储层为优质储层;部分Ⅱ_2亚类、Ⅲ_1亚类储层为中等有效储层;Ⅱ_3、Ⅲ_2及Ⅲ_3亚类储层实施酸化压裂后部分为低等有效储层;Ⅳ类储层为非有效储层。

Reasonable methods of reservoir classification and evaluation are very significant to oil and gas exploration among deep clastic reservoirs. By the study of the deeply buried Palaeogene clastic reservoirs in Dongying sag, a multi-parameter clastic reservoir evaluation method applicable to deeply buried reservoirs was concluded, which is restricted by physical property lower limit and production ability of effective reservoirs. Based on the research of reservoir characteristics and physical property lower limit of effective reservoirs, the main controlling factors of the development of effective reservoirs is analyzed with porosity difference and permeability difference as the compared parameters. By coupling the controlling factors, reservoirs can be classified comprehensively and the economic capacity of different types of reservoirs is evaluated regarding single well productivity as the evaluation parameter. Depending on superimposing different graphs, distribution of effective reservoirs can be predicted. The study results show that the deeply buried Palaeogene reservoirs in Dongying sag consist mainly of sublacustrine fan, nearshore subaqueous fan and flood-overlake. Four types of pressure system, including normal pressure, weak overpressure, medium overpressure and strong overpressure, were developed in the reservoir. The reservoirs are now mainly at middlediagenetic stage A 1,middle diagenetic stage A2 and middle stage B. Sedimentation is the most important controlling factor to the development of effective reservoir, while the controlling action of digenesis on reservoirs is based on sedimentation and formation pressure. Comprehensively considering the controlling factors of reservoirs, the deeply buried Palaeogene reservoirs in Dongying sag are divided into four categories, further into eight subcategories. Among the categories,type Ⅰ ,type Ⅱ1 and part of type Ⅱ 2 are high-quality reservoirs; part of type Ⅱ 2 and type Ⅲ are medium effective reservoirs; type Ⅱ 3, type Ⅲ2 and type Ⅲ1are inferior effective reservoirs with measures of acidization or fracturing ; type Ⅳ are ineffective reservoirs.