| 68%of proven oil reserves of the oil field where H Block is located are low permeability reserves. There are400million tons of low permeability reserves of all the unused proven reserves. However, the developing low permeability reservoirs have entered high water cut stage. In order to improve oil recovery and the unused reserves, particularly the effective utilization rate of the low permeability reserves, CO2flooding can be available, which can achieve the goals of both CO2sequestration and enhancing oil recovery. Aimed at some exposed problems at pilot site, to further study the dynamic characteristics of the CO2flooding and Injection-production capability, the analysis of responding characteristics and the study of the injection-production capability are significant for the future development of the oil fields and the prediction of later development effect.This article targeted the H block of low-permeability reservoir test area. Based on the research of CO2miscible flooding home and abroad, according to the geologic characteristics, structural characteristics and other characteristics, and so on, this paper utilized production decline, Logistic function, and four types of water drive curve, to determine recoverable reserves of test area. The recoverable reserves of H block are between40.72×104t and45.96x104t. Also this paper analyzed the change of abilities of CO2or water intake in these layers.Three typical oil-water relative permeability curves were choosed to be standardized, and the corresponding result could represent average oil-water relative permeability curve of the entire H block. Compared it with the oil-gas relative permeability curve, it could be concluded that H block is more suitable for gas flooding. This paper also analyzed the relationship between oil production index and water/gas injectivity index through relative permeability curves, and the result was that the calculated gas injectivity index was much larger than water injectivity index theoretically. Empirical formula method was used to calculate the pressure, under which horizontal and vertical fractures formed, were respectively from50.48MPa to62.05MPa and from50.48MPa to57.02MPa.The injectability of six injection wells was determined by empirical formula method and relative permeability curve with the consideration of the fracture pressure. Taking Well H4-2for example, the layered gas injection was designed according to node system analysis method. Then analysis the responding characteristics after gas injection, such as increasing of yields and gas-oil ratio, formation pressure buildup, and change of physical properties of crude oil under high pressure were analyzed.The production history statistical analysis (mainly by production decline) of response wells showed that the oil production regression rate declined from1.51%/mon before the gas injection to0.67%/mon. This implied:recoverable reserves before gas injection is about209,600tons and it was about421,100tons after WAG The static liquid level was calculated according to dynamic fluid level and production data, and then the difference between dynamic and static liquid level was treated as oil production pressure differential, solving the problem of the oil well productivity calculation. Using several models to predict the development of water flooding and gas flooding for the test area, the results indicated that the development through gas flooding that was far more better than that through water flooding. |
PDF Full Text Request