CO_2增能解堵技术在延长油矿的应用

Reservoir Blockage Removal/Pressure Boosting in Production Wells at Yanchang Oil Fields

介绍了二氧化碳增能解堵原理、所用工作液的组成和性能,及该技术在延长低渗(平均1.3×10-3 μm2)低孔(平均9.7%)油藏作为油井增产措施的应用.解堵液为加有强氧化剂的多元复合配方酸液(含有盐酸、氢氟酸、冰醋液、磷酸,浓度不超过12%);增能液为溶入二氧化碳气体的化学物溶液,在地层与酸液相遇则生成大量热和以二氧化碳为主的气体.实验配方增能解堵液与一种稠油在10 MPa初始压力下反应50分钟后,稠油25～55℃下的粘度降低90%以上;在60℃下对油井垢中分离出的硫酸钙垢、碳酸钙垢和油垢的4小时溶解率为91.0%～99.4%;初始压力10 MPa的增能液体系,经58～65分钟压力升至最高值18 MPa,此后由于二氧化碳溶于原油,压力逐渐下降.报道了施工工艺、选井及效果:解堵液、隔离液、增能液段塞分两个循环注入油井,2004年在23口油井施工,油层厚0.7～11.2米,单井注入增能解堵剂11～16吨,平均13.1吨,单井增产原油38～213吨,平均85.9吨,有效期91～131天,平均105.9天.图1表3参4.

The principles of reservoir blockage removal/pressure boosting by CO2 （BR/CO2PB）, the composition and the performance properties of the wor.dng fluids used, and the application of this combinational technology for oilwell stimulation in low permeable （1.3 × 10^-3 μm^2 in average） and low porosity （9.7% in average） reservoirs in Yanchang, North Shaanxi, are presented. The blockage removing fluid （BRF） is a polycomponent compounded mixed acidizing fluid containing hydrochloric, hydrofluoric, glacial acetic, and phosphoric acids up to 12% and enhanced by gaseous CO2; the pressure boosting fluid （PBF） is a chemical solution with gaseous CO2 dissolved under pressure and can evolve a large amount of heat and gases, mainly CO2, in contact with the mixed acids. The viscosity of a heavy crude oil is reduced by more than 90% at temperatures 25-55℃ after the crude oil having reacted with an experimental mixed BR/CO2 PB fluid at 10 MPa initial pressure over 50 minutes; 91.0-99.4 % dissolving rate at 60℃ is observed for CaSO4, CaCO3, and oily fractions of the precipitates in some production wells; at 10 MPa initial pressure, the PBF develops the highest pressure of 18 MPa in 58-65 minutes, which gradually drops down owing to dissolution of CO2 in the crude oil. The technology, ＇well selection and results of field BR/CO2PB operations are presented; the BRF, spacer, and PBF plugs are injected successively into the ,aimed wells in two cycles; totally 23 BR/CO2PB operations in 23 wells have been performed successfully in 2004 and the results can be characterized by following data： thickness of pay layers 0.7-11.2 mp; BR/CO2PB fluids injected per well 11-15 tones and 13.1 tones in averagei increment in crude oil production per well 38--213 tones and 85.9 tones in average; time duration of positive response 91-131 day and 105.9 days in average.