Efficient PDC Bit Designs Reduced Vibrational Impact While Drilling with Rotary Steerable Systems in the Geological Conditions of the Yamalo-Nenets Autonomous District

Abstract

This article is a description of a comprehensive engineering approach to new designs of PDC (Polycrystalline Diamond Compact) Bits and bottomhole equipment for efficient horizontal wells drilling in the Yamal-Nenets Autonomous Okrug (YNAO) fields with Rotary Steerable Systems (RSS) Point the Bit (PTB) type. The paper represents an analysis of the efficiency of drilling rocks of various hardness depending on the bits, the bottom hole assembly (BHA), and type of vibrations. In the Yamal region fields a main constraint of sub horizontal sections drilling performance for liner run in hole is the occurrence of vibrations. The predominant vibration types are Stick and Slip (S&S) and High Frequency Torsional Oscillations (HFTO). These types of vibrations often had to be reduced by limiting drilling regime (weight on bit (WOB), drill pipe (DP) RPM, and flow rate), which directly affected on the rate of penetration (ROP). To find solutions to this problem for drilling performance improvement, geological and geomechanically modeling of rock properties and an analysis of burst-files of vibrations (modeled in specialized software) were carried out based on downhole data. The studies have found key factors that cause the high vibration impact and reasons for premature wear of the PDC bits, which served as a basis for identifying the shortcomings of previous bit designs. Test beam experiments were also performed to assess the bits wear while drill-out of the casing accessories. The results formed the basis for development of new PDC bits designs using specialized software. As an output new 155.6/152.4 mm bits designs with an innovative cutting structure that considers the geological features and technical aspects of drilling liner sections in YNAO fields were manufactured. The new bit designs have significantly reduced vibration levels, improved ROP performance in the liner section using RSS PTB, and decreased the overall well construction time. These solutions open wide opportunities for their further implementation on other projects both in Russia and in other CIS countries.