Study On The Build-up Character Prediction Of Holding Assembly In Long Horizontal Section Horizontal Well

Unconventional energy is an important complement to the exiting traditionalenergy. Multistage fracturing technology is an effective way to developunconventional energy for long horizontal section horizontal well. Currently screwdrill, which is the main way to control well trajectory in domestic, encounter manydifficulties in drilling long horizontal segment later stage especially sliding drilling.The study on the build-up character prediction of holding assembly in long horizontalsection horizontal well can boost drilling efficiency and solve some difficulty in longhorizontal section horizontal well.In this paper, conventional BHA and screw BHA were analyzed by beam-columntheory, and the mechanical parameters of bit were calculated. The relationshipbetween drilling direction and mechanical parameters of bit, bit anisotropy, rockanisotropy though the bit-rock interaction model. The angle between drilling directionof bit and the direction of the borehole axis could be solved though rock-bit model. Anew build-up rate prediction method was presented, base on the idea of equilibriumcurvature method. BHA was deformed by the bound of wellbore, when the drillingdirection of bit coincides with the direction of the borehole axis, the paper consideredthe curvature of the wellbore as the build-up rate of the BHA. The build-up rateprediction method was different from the equilibrium curvature method. When thedrilling direction of bit coincides with the direction of the borehole axis, the newbuild-up rate could be got.On the basis of the previous analysis, the program of “The build-up characterprediction analytics of BHA” was written by VB language. By using this program, the single bend screw BHA was analyzed. The influence of some factors on the build-uprate of single bend screw BHA was studied, such as the BHA structure, the rate ofborehole enlargement, the bit and rock anisotropy index, formation dip and tendenciesand so on. The rate of borehole enlargement could weaken BHA build-up capacity,but the formation dip and tendencies could change the build up or build downcapacity.In order to meet the needs of field, the paper introduced BP neural network tobuild the relationship between theory build-up rate and real build-up rate. BP neuralnetwork was feasible in theory build-up rate with real build-up rate correction byinstances analysis on the Fan162-3HF well.