Research Weixinan Four Gas Injection Process W12-1 Oil Fields

Structure of the NO.4bore field of WZ12-1oil field middle block is relatively complete, the thickness of reservoir sand body is large (net thickness of30～80m)and has good connectivity, main drive of oil deposit is dissolved gas, the nature of crude oil is well, the average porosity is17%and average air permeability is200×10-3μm2. Due to the unsatisfactory effect of water flooding development and the limitation of offshore water injection, it is difficult to form the perfect injection-production well spacing, the recovery degree is only7.7%. In order to make full use of the rich associated gas resources in WZ area, proposed the implementation of gas injection development in the NO.4bore field. Base on the reservoir research, gas injection development plan as follows:a gas-injection well (A2well), injecting respectively to A, B and D layer, the suction ability of D layer is the best, gas absorptive capacity of A and B layer is42%of the D layer; injection volume is400000square per day, injection pressure of wellhead gas is25MPa.This paper mainly focuses on the gas injection project and making design and equipment selection for gas injection process string and surface process flow. The paper investigated literature of gas injection technology at home and abroad, as well as gas injection technology of YaHa oil field (string structure, tools, surface equipment, etc.), combining the gas injection development project of the NO.4bore field, referring to SY/T5322-2000".The design method of casing string strength", developed the disposal scheme of engineering logging for old well casing, determined the calculation method of outer, inner pressure and axial force for the old well, checking the casing strength of A2well when it is injected by gas. The calculation methods of pipe flow pressure drop are different between gas-injection well and gas recovery well, the paper refers to calculation method of average temperature-average compression coefficient, based on analysis of the wellbore pressure distribution of gas-injection well and sensitivity of tubing diameter, making optimization selection of diameter for gas injection pipe string. Combined with the experience of land oil field gas injection and the need of safety production in offshore oil field, recommending typical tools combination packages of offshore oil field gas injection string, way of tubing air-tightness. On the basis, formulating the scheme of double layering tube gas injection and single pipe gas injection in the NO.4bore field respectively. At the same time, based on the characteristics of gas injection scheme and gas source, making the gas injection surface process in WZ12-1oil field and screening of corresponding surface equipments.