Well - Resistivity Method To Determine The Oil And Gas Reservoir Boundary

The petroleum resource is the foundation of national economic development, and it is the people' s earnest dream to accelerate reconnoitring and development of the petroleum resource and improve the successful rate of the drilling well. This paper research that the range of oil and gas reservoir is located through one oil well utilizing the hole-surface resistivity method.The hole-to-surface electrical resistivity method is one of electrical prospecting methods by placing an electric current electrode in a drill hole and measuring the distribution of electric potential on the earth's surface. Compared with the surfacial electrical method, it is more sensitive to subsurface inhomogenities than arrays confined to the surface. And also, the influence of oil and gas reservoir can be stood out by caculating the difference of apparent resistivities between over the objective body and under it.At first, according to characteristic of oil and gas reservoir, the geophysical model is abstracted, the two dimensional (2-D) geoelectric model about linar current source and the three dimensional (3-D) geoelectric model about point current source is simulated by finite element software FEPG;and then, the influence of different factors is analysed. From the aspects of the depth, width, thickness of oil reservoir, the distance between point current source and oil reservoir, the resistivity difference of oil reservoir and surrounding rock, the departure of oil reservoir for the borehole, and the influence on resistivity anomaly of the high- conductivity or low-conductivity layers over oil reservoir, the laws of them are studied and the quantificational relations of are found out using the parameters of apparent resistivity and its gradient about pole-pole configuration. theoretical model analysis indicates that the hole-to-surface electricalresistivity method is feasible and effective method. For oil reservoir crossing hole, anomaly is more outstanding with the parameter of Aps',ln thepractical work, electrical current source should be made close to the oil reservoir as much as possible, and in this way, anomaly amplitude will be strengthened. When having the low-conductivity or high- conductivity layers over the oil reservoir, through the difference of apparent resistivity between over the oil reservoir and under it, the influence of low-conductivity or high conductivity layers over oil reservoir is weaken, and oil and gas reservoir is stood out, and so better result will be obtained. At last, the effectiveness of this method are demonstrated through water trough experiments.