Abstract:

Void Space Description (VSD) is a new method for quantitative recognition and prediction of faulted-related fractures targeting tight reservoir in gentle area. In this paper, this new method is applied to the study on fault-related fracture systems occurred in the Lianglitage Formation in Tazhong X well area, Tarim basin. During this course, taking Tazhong A well as an example, it is pointed out the calculation of VSD mainly include qualitative recognition of fault-related fracture by using fault plane detachment void space theory and quantitative calculation using VSD software, and the latter is composed of structure modeling, stratigraphic modeling, calibration of fracture porosity and VSD calculation. Calculation results of VSD on seismic profiles crossing three wells in the study area are proved available with cores, logging and well drilling data. Quantitative calculation for each single fault, interpreted in the study area, is conducted by using VSD technique, and the plane distribution map of maximum fracture porosity within Lianglitage Formation is obtained. There are seven effective fracture systems with relatively large scale, and the overall development and distribution pattern of fault-related fracture here are closely related to the fault system but not one-to-one correspondence. Finally, it is concluded that whether effective fracture systems are well-developed or not is mainly decided by fault plane detachment void space generated during disharmonic faulting process, that is, effective fracture systems are well-developed if there are detachment void space neighboring the fault plane in the course of faulting, conversely, it is poorly developed.

Key words: fault-related fracture, VSD technique, fault plane detachment void space, Tazhong X well area, quantitative prediction, fracture