低渗透砂岩油藏井网加密调整效果评价——以胡尖山油田H154区长4＋5油藏为例

Evaluation of effect of well pattern infilling adjustment for low permeability sandstone reservoirs

胡尖山油田H154区长4＋5油藏储层特征复杂，平面及剖面矛盾突出，且经多年注水开发后，油藏更趋于复杂。该油藏暴露出见水井逐年增多，递减大、采收率低，储层动用状况不均，剩余油分布复杂等矛盾。在现有井网条件下，常规注采调控措施已很难进一步提高油藏采收率，为此，2016年对油藏进行井网加密调整试验。在储层、油藏基本特征及剩余油研究的基础上，利用数值模拟最终优化为173m^130m不规则反九点井网进行井网加密调整。井网加密后，加密区地质采油速度提高2．6％，动态采收率提高3．5％，整体加密调整效果好。该低渗透油藏水驱后油藏物性变差，渗透率明显下降；油藏存在部分水洗，导致局部含油性变差；加密后，井网适应性好，井网有效驱替系统已建立，地层压力保持水平高；但储层改造适应性差，表现为整体储层改造强度大，见水井比例高。同时，还统计发现高压区、重复压裂改造次数多，加密井见水风险大，井网加密时要慎重。H154区井网加密调整试验的方法、思路及认识为低渗透砂岩油藏井网加密调整提供了理论依据和实践经验，值得低渗透砂岩油藏借鉴。

The Chang4＋5 reservoirs in the H154 area of Hujianshan Oilfield are of complex reservoir characteristics, with prominent contradictions in the plane and profile. After many years of waterflooding, the reservoirs tend to be more complex. Many conflicts emerged in the reservoirs, such as the increasing number of water breakthrough wells year by year, increasing production-rate declining, low oil recovery efficiency, uneven state of the oil-producing reservoirs, and complex distribution of the remaining oil. Under the existing well pattern conditions, conventional injection and production adjustment and control measures have been very difficult to further improve the oil recovery factor. For this purpose, infill drilling adjustment tests were conducted on the reservoirs in 2016. Based on the study of the basic characteristics of oil reservoirs and remaining oil, the irregular inverted nine-spot injection pattern of 173m-130m was finally adopted for optimization of infill drilling well pattern adjustment by using numerical simulation. After infill drilling of the well patterns, the oil production rate in the infill drilling zone was increased by 2.6%, the dynamic recovery rate was increased by 3.5%, and the overall infill drilling adjustment effect was good. After waterflooding in the low-permeability oil reservoirs, the physical properties deteriorated, and the permeability decreased obviously. The oil reservoirs are partially washed. resulting in poor oil-bearingness. After the infill drilling, the well pattern was well-adapted, and the effective displacement system was established in the well pattern. The formation pressure is kept at a high level; however, the reservoir stimulation is poorly adaptable, showing that the overall intensity of the stimulation is high, and the high proportion of injected water breakthrough in the oil wells. At the same time, it is also found by statistics that there are high formation pressure areas, and multiple re-fracturing. There is a high risk of water-breakthrough in the infill drilling wells. So it should be prudent when conducting the infill drilling of well pattern. The method, train of thoughts, and understanding of infill drilling adjustment experiment in the H 154 well pattern provide theoretical basis and practical experience for the well pattern＇s infill drilling and adjustment of low-permeability sandstone reservoirs, and it is worth using for reference in development of low-permeability sandstone reservoirs.