Anti-drilling Characteristic Predicting Method for Penglai Gas Area Based on Meso Characteristic of Stone

Recently years, the rate of penetration (ROP) of Xujiahe sequence of upper tertiary (13 1/8in” bores) among prospecting wells in Penglai gas area was too slow, and the difficulty in coring also constrained the process of exploration. Thus acquiring anti-drilling characteristic of Xujiahe sequence was necessary for increasing ROP and reducing the drilling costs.Based on acoustic characteristic, drillability level value, abrasiveness property, X-ray diffraction mineral components result, and microstructure property of rock samples derived from experiments conducted on outcrops and fragments of Xujiahe, the prediction method based on micro characterastics for anti-drilling characteristics was established by using results from cores as an intermediary medium. By interpreting the acoustic part of logging data after drilling by this method, Longitudinal anti-drilling characteristic profiles of Xujiahe sequence in multiple wells were revealed precisely. The results show that the drillabity and CAI abrasiveness of Xujiahe sequence is 5.79 and 2.69 in general, which means a medium hardness and a strong abrasiveness according to industry standards. Wherein, the drillabity of subordinate layers vary from 5.41 to 5.79, while the abrasiveness is upgraded about 39% when encountering T3x2. Based on the prediction results, mudlogging data and usage reports of PDC bits, advices for drilling technology template are proposed: polycrystalline diamond elements (PDE) with high impact resistance should be assembled as main elements and used with high weight on bit (WOB) & rotational speed before encountering T3x2. Afterwards, PDEs high abrasive resistance should be assembled as main elements and used with high WOB and lower rotational speed. This research pioneered anti-drilling characteristic predicting method based on micro characteristic of rock for Penglai gas area, saved one trip in Xujiahe sequence during current prospecting stage, and provided experiment and theory support for iteration and optimization on drilling templates and corresponding drilling equipment in the future.