Method for predicating oil production quantity in high-volatility oil deposit natural gas injection development

Abstract

The invention relates to a method for predicating the oil production quantity in high-volatility oil deposit natural gas injection development. The method comprises the following steps that 1), whether the injection and production conditions are balanced or not is judged: (1) if an oil deposit is subjected to static testing, whether the current formation pressure maintains the original level or not is judged; (2) if the oil deposit is not subjected to static testing, whether the accumulated injection-production ratio VRR value of the oil deposit approaches to 1 is greater than 1 or not is judged, and if so, the condition of reaching the balance state is judged; 2) the gas injection development mechanism is analyzed, and whether a target oil deposit is a miscible-phase displacement oil deposit or a non-miscible-phase displacement oil deposit or not is judged; 3) a semi-logarithmic fitting relational expression lnGi=h+mNp of the oil deposit accumulated gas injection quantity and the oil deposit accumulated oil production quantity is subjected to coefficient identification; the fitting coefficients h and m are identified according to historical data of the oil deposit accumulated gas injection quantity Gi and the oil deposit accumulated oil production quantity Np in the development process; 4) the oil deposit accumulated oil production quantity Np is predicated by adopting the semi-logarithmic fitting formula according to the reasonable accumulated gas injection quantity Gi of the oil deposit in the predicating time period. The method is applicable to the oil deposit that the oil deposit fluid is high-volatility crude oil, and in addition, the oil deposit developed in a natural gas injection pressure maintaining way is adopted.

Description

technical field [0001] The invention relates to the field of petroleum development, in particular to a method for predicting oil production in natural gas injection development of highly volatile oil reservoirs. Background technique [0002] Highly volatile crude oil is a naturally occurring hydrocarbon mixture mainly composed of intermediate components, its properties are between black oil and condensate gas, and it exists in liquid form under reservoir conditions. An important feature of highly volatile oil is that it has an obvious composition gradient, that is, the fluid composition changes with depth (the molar content of light components decreases with the increase of reservoir depth, and the molar content of heavy components decreases with the increase of reservoir depth). Another important feature of highly volatile crude oil is high shrinkage. When the formation pressure is lower than the saturation pressure, the volume of crude oil shrinks rapidly due to degassing,...

AI Technical Summary

Problems solved by technology

Due to the dual effects of composition gradient and gas injection flooding, the production gas-oil ratio increases continuously during the production process. During the development process, the gas injection displacement mechanism gradually transitions from miscible flooding before gas breakthrough to immiscible flooding after gas breakthrough. Fluid phase changes and seepage rules inside the reservoir are complex, which increases the difficulty of oil production prediction

At present, for the prediction of oil production in the process of gas injection development of highly volatile oil reservoirs, most studies rely on numerical simulation methods to predict production, but the unclear understanding of reservoirs will cause great errors in numerical simulation prediction results; and From geological modeling to reservoir numerical model, the process is complicated, the cycle is long, and the cost of personnel is high, which is not conducive to the rapid evaluation of gas injection effect and oil production prediction

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