西峰油田N区长23储集层特征及敏感性评价

针对西峰油田N区长23低渗透砂岩储集层,通过物性测试、铸体薄片、扫描电镜、高压压汞等分析,描述其储集层特征,基于岩石学特征、物性特征和孔喉结构特征进行储集层分类,同时对不同类型储集层进行敏感性评价,并分析了储集层敏感性的影响因素。研究结果表明:西峰油田N区长23储集层为细粒长石岩屑砂岩储集层,孔隙类型主要为粒间孔和长石溶孔,平均孔隙度为16.4%,平均渗透率为13.5 mD,属于中—低孔、低渗储集层;储集层可划分为3类,Ⅰ类储集层孔喉结构与物性最好,Ⅱ类和Ⅲ类储集层依次变差;研究区储集层具有中等—弱速敏、弱水敏、中等偏弱盐敏、中等酸敏、强碱敏和中等—强压敏;研究区储集层敏感性受黏土矿物、部分碎屑颗粒以及孔喉结构的影响,储集层速敏性主要与高岭石含量有关,水敏、盐敏性与伊利石含量及产状密切相关,酸敏性受绿泥石和铁白云石含量共同影响,强碱敏性是由于长石和石英含量较高导致,压敏性是孔喉结构在有效压力下发生变形,使该类储集层渗透率明显降低的结果;3类储集层的黏土矿物含量、孔喉结构以及物性不同,储集层敏感性有所差异,储集层物性由好到差,敏感性依次增强。在开发过程中应根据敏感性主控因素和不同储集层敏感性的差别,针对性地进行储集层保护,减小对储集层的伤害。

Reservoir Characteristics and Sensitivity Evaluation of Chang 23 in N Area of Xifeng Oilfield

Based on the analysis oF physical property testing, cast thin sections, scanning electron microscope and high pressure mercury intrusion for the Chang 2₃ low-permeability sandstone reservoir in N area of Xifeng oilfield, the paper describes the characteristics of the reservoir, classifies the reservoir according to petrologic features, physical properties and pore throat characteristics, evaluates the reservoir sensitivities and analyzes their influencing factors. The study results show that the Chang 2₃ reservoir in the N area of Xifeng oilfield is dominated by fine-grained feldspar lithic sandstone. The pore types are mainly intergranular pores and feldspar dissolved pores. The average porosity and permeability of the reservoir are 16.4% and 13.5 mD, respectively, which indicates the reservoir belongs to medium—low porosity, low permeability reservoirs. The reservoir can be divided into three types: the physical property and pore throat structure of Type Ⅰ reservoir are the best, and those of Type Ⅱ and Type Ⅲ reservoirs become worse and worse. The reservoir in the study area is featured with moderate-weak velocity sensitivity, weak water sensitivity, moderate-weak salt sensitivity, moderate acid sensitivity, strong alkali sensitivity and moderate-strong pressure sensitivity. The sensitivities of the reservoir in the study area are influenced by clay minerals, partial clastic grains and pore throat structures. The velocity sensitivity of the reservoir is mainly related to kaolinite content, and water and salt sensitivities related to illite content and occurrence. The acid sensitivity is influenced by both chlorite and ferrodolomite contents, strong alkali sensitivity results from high contents of feldspar and quartz and pressure sensitivity is the result of the deformation of pore throats. The clay content, pore throat structure, physical property and sensitivity of the three types of reservoir are different. During the process of oilfield development, reservoir protection should be carried out according to the sensitivity controls and the differences of sensitivity of different reservoirs, so as to reduce the damage to reservoir.