塔里木盆地库车坳陷超深层裂缝性致密气藏水封气动态评价方法

塔里木盆地库车坳陷超深层裂缝性致密气藏边底水发育，断裂、裂缝成为水侵的“高速公路”，产生“水封气”效应，降低了气藏采收率，但目前缺乏有效评价方法。为此，在分析气藏水侵特征的基础上，建立考虑裂缝发育规模、外围水体强度两因素的裂缝性气藏水封气动态评价方法，并应用于库车坳陷3个已开发的超深层区块，静动态结合对评价结果的有效性进行验证，针对性地提出了提高气藏采收率的对策。研究结果表明：①裂缝非均匀水侵受构造部位、裂缝发育程度和缝网组合方式共同控制，可划分为3种水侵模式：核部边水沿大裂缝窜进型、翼部边底水沿裂缝侵入型、低部位底水沿裂缝/小断层快速暴性水淹型；②3个典型区块水侵替换系数在0.2~0.3之间，均为次活跃水体气藏，但水封气发生的严重程度差异大，水封气越严重，气藏采收率越低；③对于方向性贯穿大裂缝型气藏，应开展堵水现场实践；对于裂缝密度高的缝网型气藏，温和开采可以控水，早期排水可以减弱水侵的影响，从而提高气藏采收率。结论认为：水封气动态评价新方法可以为库车坳陷超深层气藏裂缝非均匀水侵动态评价和气藏提高采收率提供可靠依据并支撑库车坳陷超深层气田群控水治水政策制定和经济高效开发。

Dynamic evaluation method of water sealed gas for ultra-deep fractured tight gas reservoir in Kuqa Depression,Tarim Basin

The ultra deep-buried fractured tight gas reservoir in Kuqa Depression, Tarim Basin has developed edge and bottom water. Faults and fractures have become the “highway” of water invasion, resulting in “water-sealed gas” effect and reducing gas reservoir recovery. At present, there is a lack of effective evaluation methods. Therefore, based on the analysis of water invasion characteristics of gas reservoir, a dynamic evaluation method of water-sealed gas in fractured gas reservoir considers two factors: fracture development scale and peripheral water body strength is established and applied to three developed blocks in Kuqa ultra deep layer. The effectiveness of the evaluation results is verified by static and dynamic combination, and the countermeasures to improve gas reservoir recovery are put forward. The results show that: (1) The non-uniform water invasion of fractures is jointly controlled by the structural position, fracture development degree and fracture network combination, which can be divided into three water invasion modes: The edge water channeling along the large fracture in the core, the edge and bottom water invading along the fracture in the wing, and the rapid violent water flooding of the bottom water along the fracture/small fault in the low part. (2) The replacement coefficient of water invasion in the three typical blocks is 0.2~0.3, which is sub active water gas reservoirs, but the severity of water sealed gas varies greatly. The more serious the water sealed gas is, the lower the recovery factor of the gas reservoir is. (3) For directionally penetrating large fracture gas reservoirs, field practice of water shutoff should be carried out. For fracture network gas reservoirs with high fracture density, mild exploitation can control water, and early drainage can reduce the impact of water invasion, so as to improve gas reservoir recovery. It is concluded that the new method of water-sealed gas dynamic evaluation can provide a reliable basis for the evaluation of fracture non-uniform water invasion dynamic of ultra-deep gas reservoir and enhanced oil recovery of gas reservoir in Kuqa Depression, and support the formulation of water control policy and economic and efficient development of ultra-deep gas reservoir group in Kuqa Depression.