Bit Selection In The Center Of Junggar Basin

Junggar Basin is abundant in oil and gas resources. According to analysis of past field drilling data, hard rocks in formation brought out low rate of penetration and poor drilling efficiency, which restricted the efficient development of oil and gas resources. Lack knowledge of anti-drilling characteristics and inappropriate bit which didn’t go with formation property accounts for the problem. Therefore, the research of drillability and choosing the correct bit type plays a great role in improving drilling rate.Geological information was collected as well as rock cores in the center of Junggar Basin. Indoor experiments were carried out to directly test rocks’ performance such as hardness, uniaxial compressive strength(UCS), elasticity and plasticity, Young’s modulus. The anti-drilling characteristics were studied in the paper by the analysis of experimental data in the lab, thus providing basic data for the proper selection of drill type. Single-element and multi-elemental regression model between drillability and rock mechanics parameters were established respectively, laying the foundation for drillability in actual conditions influenced by enclosing pressure, fluid filtration and so on.The interplay between acoustic travel time and rock drillability, hardness, compressive strength was discussed in the paper. On the basis of logging data, the conversion expression for the change from downhole-logged P-wave velocity to P-wave velocity of rock surface was fitted and derived, thus drillability can be directly predicted by sonic logging information. The drillability profile of several wells in the area was established according to the predicted model. Acoustic tests and cutting tests were conducted respectively to compare the effects of sizes of rock samples on the P-wave velocity measured. In addition, the relationship between drillability and P-wave velocity of cuttings can be used to estimate formation properties in the area where is lack of cores and logging data.To select proper bit type, the method called technology benefit index was firstly applied to evaluate the conventionally available bit record at offset wells. On the basis of the equal probability relationship between drillability level and bit type, the drill bit matching formation properties was chosen according to IADC code. Combining anti-drilling characteristics with on-site experience, the main cutting parameters of PDC including profile shape, cutter size, density and blade number were analyzed, providing a basis for PDC bit selection.