Study On Deep Penetration Acid Pressure Process Of High Temperature Carbonate Reservoirs

The target reservoir on the right bank of the Amu Darya has the characterestics of poor physical property, serious heterogeneity, and cracks are relatively richly developed. It belongs to high temperature and high pressure carbonate reservoir. The early stage of the acidification effect is not obvious. For the purpose of efficient development and production of the reservoir, we have to carry out targeted study of the stimulation. Acid fracturing is an effective mean of stimulation of carbonate reservoir. The current acid systems in the area can basically meet the requirement of stimulation technology. But for the specially low porosity and permeability reservoir or the reservoir which the fracture-cave is far from the wellbore, when we use the ordinary acidification or acid fracturing, the reaction rate of the acid and rock is fast, fluid loss control is poor, the effective distance of acid is short, it can only stimulate near wellbore zones. It is hard to get good production effect. We have to improve the acid system and the acid fracturing technology in order to realize the deep penertrating acid fracturing. Take the target area high temperature carbonate reservoir as the research object, for the porpurse of deep penertrating acid fracturing, we carry out theoretical study, experimental study and simulation study of the new acid system, fracture conductivity of different acid fracturing technology, fluid loss law, fluid loss countermeasures and optimization of acid fracturing technology:(1) Make an evaluation before acid fracturing from reservoir characteristics, production, early measures and so on. The requirement of acid fracturing technology and acid system to improve acid fracturing effect:the acid fracturing technology should make a goal of long fractures, low fluid loss, heterogeneous etching, high flow conductivity and the acid system should be retarded at high temperature, high efficient corrosion inhibition, low fluid loss, low damage and so on.(2) At present, the more commonly applied acid system in the area are gelled acid, VES acid, crosslinked acid, they can basically satisfied the requirment of acid fracturing. But for the specially low porosity and permeability reservoir or the reservoir which the fracture-cuve is far from the wellbore, we need to make long fractures, to achieve the goal of deep penetrating acid fracturing. According to the theoris of research study, combine the laboratory test, we further study the restarded mechanism, chelating capability, corrosion inhibition properties, thermal stability, reaction kinetics and selective etching ability. It has the surperior performance to realize deep acid fracturing.(3) We use energy dispersive system, high temperature high pressure flow conductivity tester and some other facilities to study acid fracturing type, acid system and other factors that affect the etched fracture surface appearance and the conductivity. Find out the main influence factors of etched fracture’s conductivity and provide detailed and accurate basises of acid fracturing technology and acid system selection.(4) For the characteristics of well-developed fractures, serious heterogeneity, the filtration difference of different intervals, we study the filtration law and measures to control fluid loss to improve the efficiency of acid, and put forwad the techniques which suit deep acid fracturing:the gelled fluid, removable chemical particles and biodegradable fiber.(5) Combine the target of acid fracturing. We adopt the related model to predict the production of certain etched fractures and certain fracture conductivity to optimize parameters of fractures. According to the physical characteristics in the area, we simulate the etched fracture geometry of different acid strongth, and select a reasonable acid strongth in terms of the longth of acid-etched fractures, on the basis of further study of various kinds of acid fracturing technology, combine the acid fracturing construction parameter optimization and classification standard of reservoir, we optimize the implementation plan of acid fracturing.