The Research On Dynamic Simulation Model Of Strong Loads Fracturing In Oil Reservoir

Our country's petroleum industry development now are facing embarrassing and pressing phenomenon that is the shortage of the back up reserves and the majority of the proved unexploited reserves being reserves of low permeability. Reservoir strong dynamic load fracture initiation technology has been popularized in order to effectively exploit low permeability reserves. Nowadays researches on process parameters analysis, process dynamic analysis and fracturing numbers analysis of strong dynamic load fracture initiation technology are limited which greatly restrict the technology's further development. Focusing on these problems, some work has been done in this paper. Firstly, the loading calculation model of pressure's and temperature's variation with time in the stable cubage powder's loading process. Then, on the basis of wellbore heat loss theory, the temperature and pressure variation model after deflagrating is conducted with the affecting law analysis of powder amount, powder holding structure, initial space volume and initial space's pressure to the pressure and temperature in powder deflagrating process. Thirdly, ground rock fracturing dynamic stress strength factor is introduced and thus reservoir fracturing pressure calculation model under strong dynamic condition is proposed after fracture's force analysis using fracturing theory. Fourthly, by utilizing mass and energy conservation equation, the mathematical model of fracture extension is built by coupling the following models including pressure distribution model of high pressure liquid in fracture, liquid seepage model, fracture beginning and ending criterion model, fracture extension rate model, fracture extension width model and fracture volume model. Then, by interconnecting all the sub models, the strong load fracturing dynamic simulation model connecting powder deflagrating, ground fracturing and fracture extension is built and the related computational software is programmed to carry on model coupling calculation. The results show that: the fracture's width and length increase with time; both peak pressure and fracture length will decrease with fracture number's increasing, for example, the peak pressure decreases to 63.6MPa from 108.4MPa and fracture length decreases to 1.17meters from 2.48 meters when fracture number increases to 6 from 2. Using"rock dynamic damage simulation experimental setup", 24 tests are made and the experiment results show that loading rate is the major factor that affects fracture number; the loading rate, peak pressure and fracture number under different powder parameters are calculated and the relationship equation between loading rate and fracture number is regressed which shows satisfactory inosculation when compared with the equation got from experiment. The exponential equations between fracture number and powder amount as well as powder holding structure are gained and can reach a satisfying accuracy. In this meaning, the fracture number model under strong load condition is gained. The building and research of strong load dynamic fracturing model have provided criterion of the technology's parameters'design and control, and has an important guiding meaning to the technology's further improvement and application.