Study and Application of Rock Breaking by PDC Bit in Ultra Deep In-Situ High-Temperature and High-Pressure Environment

Abstract

ABSTRACT The finite element model of the cutting tooth rock system based on ABAQUS is established by using the grid adaptive method. The average stress of each node of the cutting tooth is solved by using the secondary development of PYTHON language, and the rock breaking efficiency, real stress distribution and the influence laws of temperature and pressure of different cutting tooth shapes and rock samples are obtained. A super deep PDC bit with special non plane teeth is optimized and designed, which has achieved good results in the southern edge of Xinjiang. The research shows that the mechanical parameters of the rock change obviously under the high temperature and high pressure environment. The micro damage structure that is conducive to rock breaking by the bit is produced under the high temperature. The rock breaking efficiency is negatively related to the temperature due to the transformation of the rock from brittleness to plasticity under the high confining pressure. The double row structure of axe shaped teeth and cone shaped teeth has the best rock breaking effect under the ultra deep high temperature and high pressure environment. The drill bit footage is the longest. The problem of bit shoulder collapse is prominent under the ultra deep in-situ environment, The design of different rail double row teeth should be adopted, the design of bit stability should be strengthened, and the drilling parameters with large WOB, low speed and large displacement should be adopted. INTRODUCTION Onshore deep and extra deep layers where 39% of the remaining oil and 57% of the remaining natural gas are distributed [1-3]. The ultra deep layer in the south border region of Junggar basin is an important oil and gas reservoir and production increasing block in Xinjiang Oilfield. The reservoir in this block has deeply buried depth with high temperature and pressure, low ROP and long drilling cycle. The average well depth of the three risk exploration wells drilled in 2020 has reached 7205m, and the estimated well depth of well Matan 1 to be newly deployed in 2021 reaches even 8200m. There are extraordinary high pressure system and extremely thick salt gypsum layer in the deep well section, resulting in many complex situations, and long drilling cycle with the per-well average drilling cycle being 335d, and the average ROP of deep formation being less than 2m / h. Improving the ROP and reducing the complexity of accidents are the urgent needs and great challenges for the deep layer drilling in the south border region. Under the ultra-deep high temperature and high pressure environment in the south border region, the crustal stress increases. Affected by high temperature and high pressure, the rock crushing mechanism is extremely complex, which puts forward higher requirements for the design of bit [4].