Research On Key Techniques For Improving Drilling Speed In Haita Basin Of Daqing Oilfield

The geological structure is very complex in Haita area, the strata dip is big and the well drilling is difficult. Increasing the penetration rate and shortening the drilling cycle of the area is very important to accelerating the exploration and development process. In view of the above question, we do research on key techniques for improving drilling speed in Haita Basin from four aspects:sidewall stability, optimize drilling bits, reason analysis of drilling tools failure, micro-foam drilling fluid system.Based on the study of geologic feature in Haita Basin, by using an improved fuzzy comprehensive evaluation method, the stability of the wellface argillutite of many wells in this area was evaluated. And we found that the shale stability in this area is unstable or extremely unstable on the whole. Combining the geological characteristics of the area and the construction condition, congruent prevent caving strategy was established for this area.Combining the indoor experiment and logging data, the rock hardness and drillability level in Haita Basin were studied, and then to calculate the elastic parameter of the formation rock. Eventually the rock drillability cut plane could be assured. According to the drillability level to divide horizon, then applying drill bits comprehensive evaluation method to each layer, combining the geological characteristics of Haita Basin and the on-site drilling data the drill bits were optimized. This effectively improved the efficiency of the bit, shortened the drilling cycle and reduced the drilling cost. Aiming at the problem that the drilling tools in Haita Basin often out of work, we analyzed the vibratory form of drill string, established the mathematical model of drill string vibration. And studied its rules and the technology how to prevent drilling tools failure, and then formed a precaution technology that applicable to the Haita Basin which can lower the drilling tools'fracture frequency and improve the drilling speed in this region.Through studying the reservoir characteristics of Haita Basin, found that the major reservoirs in Haita Basin is mainly for low-to-moderate porosities, low-to-moderate and low permeability reservoirs, and the debris and clay mineral content is high. The clay mineral mainly contains illite, andreattite and chlorite. By using Single Correlation Analysis and Multiple Regression which is an ideal, fast, new method to forecast reservoir sensitivity, we received the results as follows:water sensitivity(strong), salt sensitivity(medium strong), alcalisensitivity(medium), velocity sensitivity(medium), acid sensitivity(none).In the reservoirs, the average pore throat radius is small and the pores are distributed unevenly and in complex instructures. For these factors when external fluids intrudes into the Hailaer area formation, it is vulnerable to be damaged by water sensitivity and water lock, and once damaged, it is difficult to recover. The drilling fluids used in Haita Basin currently are not good for lessening water locking and preventing caving. Therefore, on the basis of reservoir sensitivity analysis, we optimized the well compatible treating chemical and developed micro-foam drilling fluid suitable for this area. Compared with other drilling fluids used in this area, micro-foam system does well in preventing caving and rejecting. By lowering fluid column pressure, sealing pore and micro cracks and producing Jamin action at the pore throat, it can reach good plugging effect and reduced the risk of loss. That received good effect in field application by using the micro-foam drilling fluid system with anti-collapse and enhanced drilling speed properties. It efficiently controlled the accident of overcut and collapse, and the average penetration rate of test wells increased 56.7%. The applying of micro-foam drilling fluid is favor of improving drilling velocity and cement quality job. It reduced bottom-hole pressure difference and reduced reservoir damage.The above research provides solid theoretical foundation and strong technical support for improving drilling speed and speeding up exploration and development process in Haita Basin.