| Since "Nine-Five Plan" was carried out, the efficiency of exploitation of marginal three-low( low porosity, low permeability, low productivity) reservoir had become one of the important subjects of Daqing Oil Field that need to be solved. At present, in the eighth-factory area, non-producing reserves is 19510×10~4 t. Among them, Fuyang reservoir has 11485×10~4t, Putaohua reservoir has 8025 ×10~4t, and the two reserves respectively comprise 58.9% and 41.1% of the total non-producing reserves. In the area, the abundance of reserves is low and the permeability is also low, so that the exploitation is very difficult if we depend on existing technology. Aiming at these problems, we began with Putaohua reservoir and carried out the research of exploiting by horizontal well . In 2002, we finished the experiment of exploiting by two horizontal wells, and this accumulated precious experience and technology for massively exploiting by horizontal well and for the efficiency of exploitation of non-producing reserve.According to the basic theory of horizontal well percolation theory, this paper derived the velocity potential distribution of infinite reservoir boundary 3D steady percolation. On the basis of image theory and interpolation principle derived a 3D steady potential distribution from bottom water drive horizontal well. And this paper deduced a 3D steady productivity new equation. Considering the influence of the location of horizontal well in the reservoir and formation anisotropic, the new equation makes productivity equation more ease and more practical by introducing a flow resistance coefficient.According to basical percolation theory of horizontal wells, this paper researched the problem about water coning and critical rate of horizontal wells. Primary research results : the high flow ability ratio and low flow ability ratio cause different product performance. After water appeared, the recovery ratio of vertical wells is lower than that of horizontal wells. When flow ability ratio is high, the recovery ratio of both ranges from 1.5 to 3, even to 8. But the difference of both is small under higher flow ability ratio.This paper has also studied the inflow performance of the horizontal well. When pressure drawdown in the well bore is high, that is to say, there is only single-phase flow in the formation and well bore. The IPR curve of the horizontal well is not a straight line, but a curve. The higher the pressure loss in the well bore is, the more obvious the IPR curve of the horizontal well deviating the straight line is. To the bottom water reservoir or gas-cap reservoir, the well bore diameter should be increased in order to reduce pressure drawdown in the well bore of the horizontal well, which can lag the coning of the bottom water of bottom gas.In the process of horizontal wells' design, we used the multi- Profession research approach, such as seismic interpretation, geological modeling, numerical simulation, economic evaluation and so on, to know clearly the reservoir's characteristic of the area that will be developed by horizontal wells, optimized the design of well location and predicated the productivity and economic profit of exploiting by horizontal wells. In the process of drilling, we used all kinds of technologies and methods, such asLWD monitor system, debris logging and so on, to carry out real-time monitoring, and this enable us to drill in the thin oil reservoir whose thickness is less than 2 meters and successfully cross little faults, and achieved the second landing. After produced, the two well both achieved good result. At present, they are being produced at ration 1:1 of injection and production. At the same time we carried out numerical simulation work and researched the feasibility of further decreasing the investment to horizontal wells. In addition, we demonstrated the feasibility of exploiting by horizontal wells in Fuyu reservoir. |
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