长庆高矿化度致密油藏空气泡沫驱适应性研究

Adaptability of Air Foam Flooding in High Salinity Tight Oil Reservoirs of Changqing Oilfield

开展了空气泡沫驱提高裂缝发育高矿化度致密油藏采收率的实验。利用自主研发的高温高压泡沫装置评价泡沫剂的发泡能力、半衰期及抗盐性,考察了气液比对泡沫稳定性的影响;通过物理模拟装置研究空气泡沫驱在基质岩心的注入能力、驱油效率及改善裂缝渗流的能力。结果表明,SFR-173阴离子-非离子复配发泡剂在去离子水和模拟地层水中的泡沫体积分别为290和340 m L,半衰期分别为368和330 min,泡沫综合指数分别为6370和6697,泡沫性能最好。当矿化度由7增至56 g/L时,0.5%SFR-173发泡剂的泡沫体积由370降至340 m L,出液时间由174缩短至122 s,半衰期由778减至330 min。地层条件下,泡沫体积随气液比增大而增大并逐渐稳定,最佳气液比在1∶1~2∶1之间。致密油藏空气泡沫注入性研究结果表明,随注入体积的增加,岩心两端压差和阻力系数增大并逐渐稳定,最大值分别为31.4 MPa和1.74;水驱后转空气泡沫驱,驱油效率提高17.86%。在裂缝非均质油藏条件下,水驱含水率达98%时的采收率仅为39.14%,水驱后转空气泡沫驱能有效改善基质岩心的动用状况,封堵裂缝渗流通道,基质岩心采收率分别从12.59%和21.21%提高至49.87%和72.0%。

The improving oil recovery experiment of fracture dense high salinity reservoir was carried by air foam flooding. The ability of foam foaming agent,the half-life and salt resistance,and the effects of gas-liquid ratio on foam stability were evaluated by use of self-developed high-temperature and high-pressure device. The matrix core injectivity of air foam flooding,oil displacement efficiency and the ability of improving seepage cracks were researched through physical simulation device. The results showed that the foam volume of SFR-173 anionic-nonionic foaming agent in deionized water and simulated formation water was290 and 340 m L,the half-life of that was 368 and 330 min,and the foam composite index was 6370 and 6697,respectively,indicating best foam performance. When the salinity increased from 7 to 56 g/L,the foam volume of 0.5% SFR-173 decreased from370 to 340 m L,producing liquid time decreased from 174 to 122 s and the half-life reduced from 778 to 330 min. Under the formation condition,the foam volume increased and became gradually stable with increasing gas-liquid ratio. The optimum gas-liquid ratio was between 1∶1 and 2∶1. Air foam injection results in dense oil reservoir showed that with the increase of injection volume,the core pressure at both ends and the drag coefficient increased and became gradually stable,and the maximum value was31.4 MPa and 1.74,respectively. The oil displacement efficiency increased by 17.86% after water flooding transferred to air foam flooding. Under the condition of crack heterogeneous reservoir,the water flood oil recovery was only 39.14% when the moisture content was 98%. The air foam flooding could effectively improve the utilization of core matrix condition and seal cracks seepage channel. The oil recovery of matrix core increased from 12.59% and 21.21% to 49.87% and 72.0%.