Study Of The Karamay Nine Carboniferous Reservoir Of Heavy Oil Reservoir Modification Technologies

The Carboniferous system heavy oil reservoir in the ninth district of Karamay is of specific characteristics. According to the properties of geology and fluids in the reservoir, it is considered as a fracture reservoir. And the oil viscosity, which is high in the west part while low in the east part, is commonly lower than that of ordinary heavy oil (40-300mpa.s). Compared with the heavy oil (the viscosity more than 2000mpa.s) produced by the thermal recovery, it is more closed to thin oil. Furthermore, in the ninth district Carboniferous system heavy oil reservoir, there are many natural fractures and the drilling fluids have universally polluted production wells. Moreover, the wells were all casing completion and the near-well-bore fractures were heavily closed off, which resulted in the low production rate of several wells during the initial formation testing. In view of the heavy pollution in the near-well-bore area, the permeability and production rate of this area can be improved through the oil formation reconstruction before producing. Additionally, the lithologic compositions of the Carboniferous system formations are mainly sandstone, erinaceous shale and bedded tuff. Thus, either hydraulic fracturing or matrix acidizing could theoretically result in a production increase. However, in reality, the acidizing results were not obviously; the hydraulic fracturing did not result well in all the wells, too. Therefore, the key points will be discussed in this paper are the suitability and reasonable treatment scale in the hydraulic fracturing and matrix acidizing applied to the ninth district Carboniferous system formations.This research was applied to resolve the problems of the heavy oil formations in the ninth district Carboniferous system. It was in accordance with concrete features of the heavy oil fracture reservoir and proceeded from both the exploitation history and production characteristics of the reservoir. During the research, the following approaches were involved in: reservoir engineering, numerical simulation, production engineering and entry fracturing design etc. Firstly, the feasibility and main technologies of the oil formation reconstruction in the reservoir were cleared and definite. Then, in view of the geological features (complex in-situ rock mass structure, frequent earthquake surrounding the oilfield and the complex tectonic stress field characteristics), the value and direction of the terrestrial stresses were carried out with the modern terrestrial stress characteristics, which supplies the stimulation approaches with technical support. Finally, the pilot area was selected out based on the pilot areaexploitation and designing principles; also, the fracturing scale was optimized and the fracture fluids & proppants were selected out, proceeding from the area entire reconstruction.