| Since 1999, a new recognition of mineral was got from X diffraction analysis during the course of well stimulation research in Qingxi , Yumen oil field. According to the result of core analysis, the content of continental detrial rock is 35. 15%, carbonate is 33.84%, and clay mineral is 31.01% in the formation. It is characteristic that three main compositions is one third of total mineral separately. Therefore, it was named geological shale dolomite and dolomite mudstone and etc... In the view of engineering, this type formation is not only different from ordinary carbonate rock, but also sandstone, which result in big changlleges such as how to optimize stimulation method and select acid fluids. After two literature retrievals by information research institute of CNPC in 1999 and 2000, it was concluded that no report of stimulated this kind of formation. To the technological problems faced in complicated fractured formation, a new research development of stimulation in carbonate reservoir was investigated and summarized. After having done research and application done for several years, a technological creation were as following:1. A new formation was named from engineer that is complicated lithologic reservoir, the definition of which is the rock that has relative even contents of detrical rock, carbonate, clay mineral, or equilibrium ratio between some mineral and two others, different from the reservoir of main carbonate or metrical rock content. This name was admitted by petroleum engineer and applied2. A novel method of formation evaluation before acid fracturing was presented. The content of detrical rock, carbonate and clay mineral were tested by utilizing the whole-core analysis technology from the view of engineering. The Content of clay was tested by the means of X diffraction analysis, and also potential damage factors were analyzed. Micro-structure was observed by ESEM(Envoirmental Scanning Electron Microscope). Natural fractures were analyzed by FMI logging. Formation stress was calculated by array sonic logging to predict the height of acid fracture, and so to make out the formation evaluation technology before corresponding stimulation for this special reservoir.3. An experimental method of acid rock reaction kinesthetic was set up to get reaction equation between acid and complicated rock, we have done systematic research of acid rock at high temperature to get actual acid rock reaction law, which including various temperature such as 50℃ 90℃. 120℃, different acids such as ordinary acid, gelled acid,emulsified acid, and also the factors of acid type, reaction temperature, acid concentration, acid velocity and so on. It showed that reaction rate of acid/complicated rock is 1/10-1/100 of reaction rate for conventional carbonate reservoir.4. Acid rock reaction pattern was studied. Traction period of acid rock reaction was talked about at varies temperatures, acid types and rotating velocities. And factors affected to H+ diffusion factor were analyzed. The result showed that Traction condition was different at the various temperatures. To high temperature, change point doesn' t appear, acid rock reaction is always at the pattern of surface reaction controlled kinetics. With rotating velocity increased, reaction rate of gelled acid keep low rate and increased slowly and then it increased sharply at 1100 rpm, which result in different affection on reaction rate. Reaction mechanism is needed to study further.5. An experiment method of acid etched fracture conductivity was set up for in-situ multistage acid fracturing. The result was compared carbonate reservoir with complicated lithology reservoir. Acid etched pattern was studied in the condition of various minerals. Based on the result of experiments, a novel acid fracturing technology was presented for complicated lithological reservoir.6. A new model evaluated pressure drawdown was set up considering acid wormhole. The software of acid fracturing pressure drawdown was finished. An evaluation technology on the bases of acid fracturing pressure analysis comes into being, which improved technology level of acid fracturing.7. Multistage pad acid fracturing simulated software was developed, 32 times optimized designed finished. And then the treatments were carried out in Yemen Ingrid oil field, Qinghai Gas oil field and Shizigou oil field and etc. By pilot tests in the oil field for several years, a new stimulation technology pattern was developed for complicated lithology reservoir, including three main combined technologies as following: combined technology of"gelled acid fracturing + multi-component acid closed fracture acidizing" , combined technology of" preflush acidizing+ gelled acid fracturing+ emulsified acid fracturing" , combined technology of" emulsified acid fracturing+multi-component closed fracture acidizing. "8. Application in Yumen Qingxi oil field, Qinghai Gas oil field got obvious economical and social result by using the new acid fracturing technology. It is not only presenting stimulation method suitable for complicated lithology reservoir, but also contributing to enhance reserves and production for Petrochina. Oil production per year of Yumen qingxioil field was up to 450 thousands tons, in which economical profit got by acid fracturing was great than 3 billions Yuan and increment oil was beyond 70% of total production. It showed good prospects and got good economical benefits and social results.
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