Abstract:

In broad gentle structure regions of both compact carbonates and sandstones, some fault-related fracture (FRF) traps are important domains for hydrocarbon exploration. However, the qualitative and quantitative identification of FRF is still difficult in structural geology. In this paper, a new method for qualitative identification and prediction of FRF, based on fault detachment theory, was introduced. With the establishment of replacement model between fault plane void space and FRF, qualitative identification and prediction of FRF can be carried out through observing the combination structural features among top and bottom surfaces of the fault and its fault surface. Taking Zhonggu 3 and Tazhong 72 wellblocks as examples, qualitative identification of FRF was firstly conducted for the Upper Ordovician Lianglitage Formation in both vertical seismic profiles and in plane. The predicted result based on fault detachment theory was compared with those results from logging and seismic attribute analysis, respectively. The results show that the predicted results are basically consistent with those revealed from logging data, and the plane distribution results are almost consistent with the overall characteristics obtained from RMS, with difference in details. It indicates that the fault detachment theory can be effectively used to qualitatively predict the FRF. The fault detachment theory, not only provides a new qualitative evaluation idea and method for the development distribution of FRF both ground and underground, but also provides an important theoretical basis for quantitative characterization of FRF.

Key words: fault-related fracture, qualitative identification of fracture, fault detachment theory, fracture