东海盆地西湖凹陷西次凹天然气资源分级评价

Grading evaluation of natural gas resources in the western sub-sag of Xihu Depression,East China Sea Basin

东海西湖凹陷天然气资源丰富,呈现出常规、低渗和致密气并存的特点,但以往的资源评价仅预测总资源量,未区分常规、低渗和致密气资源量,不能满足油气勘探开发实践的需要。以西湖凹陷内油气勘探与发现程度相对较高的次级构造单元西次凹为研究对象,在合理求取各项参数的基础上,选用容积法对西次凹已发现气藏的常规、低渗及致密气资源分别进行了定量评价,并探究了资源分级分布规律及其主要控制因素。研究表明,西湖凹陷西次凹天然气资源丰富,总体呈现出“致密为主,少量低渗”及“中浅层低渗,中深层致密”的分级分布规律;资源分级分布受多种因素的联合控制,其中储层是基础,烃源是关键。研究成果有助于探索建立适用于西湖凹陷天然气资源分级评价的方法技术,并可为研究区天然气勘探开发部署与决策提供科学依据。

The discovery of abundant natural gas resources in Xihu Depression of East China Sea Shelf Basin revealed the characteristics of the coexistence of conventional,low-permeability and tight gas resources.However,the previous resource evaluation only predicted the total resources and did not distinguish among conventional,low-permeability and tight gas resources,thus failing to meet the needs of oil and gas exploration and development practices.This paper takes the western sub-sag as the study area,which is a secondary tectonic unit with relatively high oil and gas exploration and discovery in Xihu Depression.On the basis of reasonable selection of various parameters,the"volumetric method"is used to quantitatively evaluate the conventional,low-permeability and tight gas resources of the gas reservoirs discovered in the western sub-sag,and discusses the rules and the main controlling factors of the distribution and grading of natural gas resources.The research shows that the western sub-sag is rich in natural gas resources and the rules of"the tight gas content is the highest and contains a small amount of low-permeability"and"low-permeability gas is distributed in the middle and shallow layers when tight gas is distributed in the middle and deep layers".The distribution and grading of resources is controlled by a combination of factors,where the reservoir is the foundation and the source of hydrocarbons is the key.The research results will help to explore and establish the method and technology applicable to the grading evaluation of natural gas resources in Xihu Depression.It will provide scientific basis for natural gas exploration and development deployment and decision-making in the study area.