DERIVATION OF MATERIAL BALANCE FORMULA OF FRACTURE-CAVITY RESERVOIR AND OPTIM IZATION OF CALCULATION PARAMETERS BASED ON ENVIRONMENTAL REQUIREMENTS

摘要

To accurately obtain the geological reserves of fracture-cavity carbonate reservoirs, the material foundation of the reservoir should be implemented. Based on the conventional material balance formula of the reservoir, the material balance equation of four types of oil-water models: closed constant volume non-aqueous fracture-cavity unit, non-closed water body with intrusive fracture-cavity unit, closed water body fracture-cavity unit, closed water body and wa-ter invasion fracture-cavity unit is introduced. In view of the particularity of fracture-cavity reservoirs, the percentage of closed water of the total volume of fracture-cavity is introduced. The two parameters that have less influence on the calculation results, such as the bound water saturation and rock com-pression coefficient, are removed. The formula for calculating the material balance of fracture-cavity reservoirs under the 4 types of oil-water model was re-derived. At the same time, in order to improve the accuracy of the calculation of the material balance formula, when calculating the compression coeffi-cient and volume coefficient of crude oil, the method of linear fitting will be used to introduce the sensitive parameter of pressure change to establish the rela-tionship between the compression coefficient and the volume coefficient of crude oil and the gas-oil ratio and pressure, respectively. Taking the Halaha- tang fracture-cavity oil field as an example, the cal-culation results show that the average error between the fitting results of the compression coefficient and volume coefficient of the crude oil and the laboratory measurement results is 4.7% and 1.9%, respectively, which can more accurately calculate abnormal high pressure and deficient reservoirs reserves. The newly derived fracture-cavity reservoir material balance formula is more suitable for the calculation of re-serves in fracture-cavity type reservoir.