塔河强底水砂岩油藏注CO_(2)+N_(2)混合气提高采收率室内试验研究

Laboratory experimental study on enhanced oil recovery by CO_(2)+N_(2) mixture injection in Tahe sandstone reservoir with strong bottom water

塔河油田A区三叠系下油组油藏是典型的断块强底水砂岩油藏,具有底水能量强、高温高盐、水淹后治理难度大的特点,继续注水开发或化学驱开采效果不佳。针对这一问题,结合塔河强底水砂岩油藏的实际情况,开展了室内注CO_(2)+N_(2)混合气驱替抑制水锥以及混相作用的三维物理模型试验研究:先底水驱替至产液含水率为88%,再考察不同注气方式、不同注气速度、不同注采部位注CO_(2)+N_(2)混合气的增产效果及对采出程度的影响。研究结果表明,采用注CO_(2)+N_(2)混合气驱替原油可以有效提高原油的采收率,当产液含水率达到88%时,原油的采收率为32.8%;段塞体积比1∶1水气交替注入提高采收率为14.38%,比连续气驱提高采收率(13.37%)高1.01个百分点;注气速度为1、2、4mL/min的提高采收率依次为11.65%、15.28%、13.40%;顶部注气底部采油的提高采收率为15.54%,比底部注气顶部采油提高采收率(13.4%)高2.14个百分点。该研究为CO_(2)+N_(2)混合气驱替在油气开采中的实施和应用提供了可靠的试验依据。

The lower Triassic oil reservoir in Block A of Tahe Oilfield is a typical fault-block sandstone reservoir with strong bottom water,which has the characteristics of strong bottom water energy,high temperature and high salt,difficult treatment after water flooding,and poor effect of continuous water flooding or chemical flooding.In order to solve the problems,combined with the actual situation of Tahe sandstone reservoir with strong bottom water,the 3D physical model experiment study of CO_(2)+N_(2)mixture injection to inhibit water cone and miscible function was carried out.The bottom water was driven to the water content of producing liquid of 88%,and then the effects of CO_(2)+N_(2)mixture injection in different gas injection methods,different gas injection rates,and different injection and productionpositions on the stimulation and recovery degree were investigated.The results show that using CO_(2)+N_(2)mixtureinjection to replace the crude oil can effectively improve the oil recovery,and the oil recovery of crude oil is 32.8%when the water content of production liquid reaches 88%;The enhanced oil recovery by the slug volume ratio of 1∶1 water alternating gas injection is 14.38%,1.01 percentage points higher than that of continuous gas injection(13.37%);The enhanced oil recovery for the gas injection rates of 1,2,4mL/min is 11.65%,15.28%,13.40%,respectively;The enhanced oil recovery of bottom oil recovery by top gas injection is 15.54%,2.14 percentage points higher than that of top oil recovery by bottom gas injection(13.4%).This study provides a reliable experimental basis for the implementation and application of CO_(2)+N_(2)mixture gas displacement in oil and gas exploitation.