Evaluation On The Adaptability Of Underbalanced Drilling Speed ​​in Yuanba Area

It is rich in natural gas resources in Yuanba region, which has tremendousexploration and development potential and will be drilled on a large scale. But the region has these characteristics such as gas reservoir buried depth, high formation temperature, high pressure and rock density, resulting in drilling difficultly and with high risk. According to the need of engineering and all kinds of complicated situations in the course of drilling, we need to carry out the relevantresearch on engineering geological characteristics and the drilling technology countermeasures, so as to promote all kinds of constructionsuccessfully, and furtherly provide support and technical reserves for exploration and developmentwell process scheme and optimization in Yuanba region. To promote the area on a large scale exploration and development work also has important practical significance.Based on rock mechanics, the model andprofile for prediction created by tensile strength, compressive strength, cohesion, angle of internal friction, elastic modulus, Poisson’s ratio, which are all calculated by logging data, proved that formation in Yuanba region shows high density and intensity, and poor drillability. Prediction model and profile of pore pressure in Yuanba region are established via Eaton method with the data provided by normal compaction trend. Prediction model of in-situ stress profile logging is built by inversion of wellbore instability and hydraulic fracture on the basis of in-situ stress acoustic emission experiment. Direction of horizontal in-situ stress is found via analyzing formation dip and image logging. Accurate formation collapse pressure and fracture pressure is calculated by studying borehole instability, which raises the rate of safety and efficiency in the course of drilling in Yuanba region. Based on response characteristics, this paper optimizes the characteristics parameters, establishes a method about evaluating feature of production zone in rock groups, including Ziliujin formation and Shaximiao formation.In combination with the engineering geological basic theory research in Yuanba region, form the countermeasures of a complete set of optimized drilling technique; Through the optimization of well bore structure, give full advantages to the foam drilling, air drilling, liquid underbalanced drilling and efficient power drilling tools, and tracka complete set of optimized drilling technology, which has got a good validation inspeeding up effect; And then it plays a certain guiding significanceto accelerate the exploration and development process for Yuanba region.