Horizontal Well Sealed Coring Technology Research

With the great area development of horizontal well,the coring techniques matched with horizontal well drilling and completion technologies are taking an irreplaceable role. They are of great significance for studying the tertiary recovery effect of horizontal well, studying the internal structures of point bar sands and the relation of the distribution of lateral accretion with the distribution of remaining oil. They can provide basis for exploring the effective methods to tap the remaining oil on the top of thick oil reservoir under the condition of vertical well.Sealed coring technology can obtain the cores free contaminated from drilling fluid and series of geologic data such as the accurate oil or water saturation. It plays an important role during oil or gas development and reserve assessment. With the development of the thin zones with low oil abundance by using horizontal wells, in order to improve per well production, reserves producing level and the development effect of target zones, studying the principle and way of horizontal-vertical well pattern must obtain more accurate geological data of cores using continuous sealed coring technology for horizontal well.This paper analyzes the difficulties of horizontal well sealed coring technique. Horizontal well sealed coring tools have been designed according to the stress analysis of the drilling tool inside the horizontal section and the theory of sealed coring. Four types of BHA which can adjust well trajectory during coring have been designed by establishing and evaluating the theoretical model. High efficient synthetic sealed fluid has been developed through laboratory studies. The tests on site have verified effectively the coring tools, BHA, the synthetic sealed fluid. A set of sealed coring techniques for horizontal well which are suitable for the characteristics of the horizontal wells in Daqing have been formed. The tool instructions and operating procedures have been worked out.The research of this subject is a good supplement of the existing coring technologies. It improves horizontal well drilling techniques. It is very important to develop reasonable exploration and development program, to enhance oil recovery and tap the deliverability of the oilfield.