断层封闭性评价及断圈含油气预测

Evaluation of fault seal and hydrocarbon potential prediction of fault traps

在全面剖析断层封闭机制的基础上,提出针对不同封闭机制的断层封闭性定量评价方法,明确控制断层圈闭油水关系的控制因素。研究结果表明:断层封闭机制主要是物性封闭和水力封闭,其中物性封闭包括3型5类:即岩性对接封闭、断层岩封闭(碎裂岩封闭、层状硅酸盐-框架断层岩封闭和泥岩涂抹封闭)和胶结封闭。针对不同封闭机制提出3种定量评价方法:基于岩性对接封闭提出的利用Allan图解定量评价断层封闭性方法;基于断层岩封闭提出的利用SGR定量评价断层封闭性方法;基于断层稳定性提出的利用临界流体压力定量评价断层封闭性方法。决定断层圈闭油水分布的关键是断层侧向封闭能力,但成藏期后断层活动也会导致大量油气散失和调整。对于致密储层而言,通常是岩性对接和断层稳定性决定断层圈闭油水分布;而对非致密砂泥互层储层而言,通常是断层岩封闭和断层稳定性决定断层圈闭油水分布。

Based on the overall analysis of the fault seal mechanism, the quantitative evaluation methods of fault seal for different fault seal mechanisms were proposed, and the controlling factors of oil-water relationship of fault traps were determined. The results show that the main fault seal mechanisms are property sealing and hydraulic sealing. The property sealing includes three types and five classes： the lithology juxtaposition sealing, fault rocks sealing（cataclasite sealing, phyllosilicates-framework fault rocks sealing and clay smear sealing） and cementation sealing. According to the different seal mechanisms, three quantitative evaluation methods are presented. First, the sealing of faults with the type oflithology juxtaposition sealing can be evaluated quantitatively by use of Allan graph; second, the sealing of faults with the type of the fault rocks sealing can be evaluated quantitatively by use of SGR value; third, based on the fault stability, the sealing of fault is evaluated quantitatively by use of the pressure of the critical fluid. The key to control the oil-water distribution of fault traps is the fault lateral seal ability. However, the fault activities will also lead to a lot of hydrocarbon dissipation and adjustment after accumulation period. For the tight reservoirs, the oil-water distribution of fault traps usually is controlled by the lithology juxtaposition and fault stability, and for the non-tight sandstone and mudstone reservoirs, the fault trap oil-water distribution is usually controlled by the fault rocks sealing and fault stability.