The Characterization of Carbonate Fracture-Cavity Reservoirs in Tahe Oilfield

Abstract

Tahe oilfield is the typical carbonate fracture-carvity reservoir in the north uplift of Tarim Basin, western of China. Caves and fractures are the main reservoir space. The reservoir has characteristics of very strong heterogeneity and is difficult to quantitative characterization. In this paper, taking Tahe block 4 and block 7 as an example, we present a systematic method to characterize the carbonate fracture-cavity reservoir. According to outcrops, cores, logging data, seismic data and dynamic data, we classified the reservoir into caves, pores, large scale fractures and small scale fractures. Then we analyzed the connectivity of reservoirs based on dynamic data, defined the boundary of the fracture-cavity unit and divided it into different units. Block 4 is divided into 8 units, and block 7 is 5 units. The cave is the most important storage space of fracture-cavity reservoir. Taking the typical units as an example, in order to describe the internal architecture of caves detailed, we divided the caves into underground rivers, isolated caves, and doline caves based on the genetic mechanism and size. Then the size and shape, internal filling characteristics, mutual dispose relationships and communication status of underground rivers, isolated caves, doline caves, pores, large fractures and small fractures are characterized detailed integrating static data and dynamic data for further refinement of the fractures and caves. On the basis of architecture anatomy, the pattern of fracture and water surface both controlling facies distribution and the pattern of water surface mainly controlling facies distribution are summarized. Combined with the fracture-cavity fabric geometry constraint parameter and different fabric configuration of different elements, the patterns are used to assist establishing the facies model. It can be used to be the guidance of karst facies modeling. For the single well, the standards of the filling type and the filling degree of caves are established quantitatively with cores calibrating logs. The quantitative characterization method of property parameter in different fracture-cavity units is set up based on different filling characteristics, and the parameter distribution and controlling factors are revealed. The filling characteristic of caves under different karst background is different, leaing to distribution of property parameters. This can be used to make property model.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015