Process Technology Research Vuggy Carbonate Reservoirs Density Selective Water Shutoff

Currently, application of water shutoff agent in fractured-vuggy reservoir in Tahe oilfield has two problems. On one hand, the density of high strength plugging agent is high and the loss of it is fast, furthermore it is non-selective plugging agent and has poor reservoir adaptability. On the other hand, the strength of selective water shutoff agent is insufficient, it is difficult to meet the need of high flow capacity in high heterogeneity reservoirs. In addition, the problem that the selection of well which implement plugging is unscientific and plugging process is not complete severely restricted the application of water shutoff agent in Tahe oilfield. This paper launched corresponding research on the basis of the survey of research status of blocking agent in limestone, and made the following main understanding:(1)By taking researvoir tolerance, strength and selective into account, this paper developed the plugging angent which can meet the characteristics of limestone reservoir in Tahe; we get the water shutoff agent formulation that can meet the reservoir condition in Tahe and whose density is between formation water and crude oil through experimental research. This paper also evaluated its response time, strength and other properties.(2)For the characteristics that fractured develop, reservoir space is large and density exchange is fast with gravity dominating, this paper developed a new ultra-low density solidified particles (density which is between formation water (1.14g/cm3) and crude oil is1.09-1.13g/cm3) which does not shrink before and after curing and can resist oil and water dispersion. This makes the blocking agent reside in the oil-water interface effectively and automatically spread, then form a barrier to block bottom water after cuing.(3)Combined with the actual characteristics of Tahe oilfield, this paper obtained a supporting well selection method in fractured-vuggy reservoir in Tahe oilfield, and foamed three kinds of plugging well selection methods from qualitative to semi-qualitative and back to qualitative, they are:five basic analysis method, weight method and network method. Meanwhile, for different characteristics of plugging process, we analyzed the adaptation of various processes in different reservoir conditions and formed promoting crosslinking to plug process, high strength sealing process, mild acidification and other processes.(4)According to well selection methos, this paper optimized TH10421, TK838and other8wells to inject water shutoff agent by analyzing single well dynamic-static data, analyzing the characteristic of water breakthrough and the potential of the measures. The production of6wells significantly increased (higher than400t), the efficiency is75%and the cumulative oil production is8750t.This paper focused on the ultra-low density solidified particles and initially formed the density plugging process with Tahe oilfield specialty. This process provided a certain guide to Tahe oilfield and other similar oilfield.