The Technology And Application Of Marine Carbonate Gas Reservoir Acid Fracturing In Northeast Sichuan

The marine facies carbonate gas reservoirs in northeast Siehuan province include two blocks of Tongnanba structure and Daxian-Xuanhan district.The ascertain gas bearing areas are separately 2919.01km² and 1116.089km²,ascertain gas geologic reserve is 2510.70×10⁸m³, controlled reserve is 1306.34×10⁸m³,and prognostic reserves 1914.70×10⁸m³.So it is significant territory of exploratory development of marine facies carbonate and the main gas source region in southwest branch company According to the scheme of transmitting the gas of Sichuan to the east and the want of downstream market,it's necessary to quicken the safe and high performance development of gas reservoir.Aeidizing or acid fracturing is imperative stimulation technology for developing marine facies carbonate gas reservoirs based on the over year experiences home and abroad.So the acid fracturing technology is also the effective method for gas development in Tongnamba district.But there are some difficulties for acid fracturing in northeast Sichuan such as complicated geologic condition,abundant natural fracture,high sulfur content,and large reservoir depth and so on.Furthermore,there is little experience of acid fracturing in this area,so it's necessary to do some researches into the acid fracturing technology suitable for the reservoir in order to improve gas production and recovery ratio.Based on the survey and study of literatures home and abroad,and in view of the geologic characteristic,iron and sulfur control technology and improving acid fracturing effect technology,this paper attains some research outcomes as follow:(1) Through the analysis of geologic information,log data,well logging data and testing data of marine facies carbonate gas reservoirs in northeast Sichuan province,this paper proposes the construction demand of acid fracturing technology in this reservoir.(2) Based on the chemical thermodynamics and ionic equilibrium theories, systematically compare and analyze the deposition behavior of Fe²⁺,Fe³⁺ in conventional condition and hydrogen sulphide condition,and propose a new clue of controlling iron and sulfur in gas well with sulfur.In view of the technology problem of acid fracturing in the formation with sulfur and the physics and chemistry character of hydrogen sulphide,this paper proposes three addition agents which are ferrous stability,sulfur control agent and hydrogen sulphide absorbent agent for acid fracturing in gas well with sulfur,which solves the deposition problem of sulfur and iron.(3) Develop a new gelling agent for acidic condition and cross linking agent with high viscosity and strong temperature tolerance,optimize clay inhibitor,ferrous stability,acid corrosion inhibitor and discharge aiding agent to form a new acid group fracturing fluid system,and evaluate some technology parameters and performance of the fluid system such as rheology behavior,friction resistance,proppant carrying capacity,corrosion control,fluid loss,viscosity break and so on.The evaluation results show that the fluid system has good retarded and shearing ability;Furthermore,it can decrease the fluid loss and friction resistance so that the performance of flowback is good.Because of the good performance above,the fluid system is suitable for the marine facies carbonate gas reservoirs in northeast Sichuan province and has good application foreground.(4) In view of the effects of pressure drop,fluid gravity,earth stress gradient and difference and so on,and based on longitudinal mass transference,the triaxial calculation model of acid concentration distribution is established.(5) Through the survey and study of acid fracturing technology,and combined with the geologic characteristic in this area,this paper proposes the acid fracturing technology suitable for marine facies carbonate gas reservoirs in northeast Sichuan province.Based on the demand of construction and allied technique research,this paper forms systematic acid fracturing technology which has attained successful application.