THROUGH BIT LOGGING: A NEW METHOD TO ACQUIRE LOG DATA, AND A FIRST STEP ON THE ROAD TO THROUGH BORE DRILLING

摘要

Through Bit Logging (TBL) has been developed over the last few years by Shell and Reeves Oilfield Services (together with industry partners) as a cost-effective and operationally efficient alternative to standard wireline conveyance and LWD. In the new system the logging tools are conveyed via the drillstring and pass into open hole through a specially designed bit, with formation evaluation data being acquired with wireline tools for surface readout, or with memory tools while tripping drill pipe out of the well. The Reeves logging tools are latest technology, small diameter (2.25-inch OD) oilfield tools with low power consumption suitable for both wireline and battery-memory operations. They have completed 17,000 non-TBL operations, providing mainly quad-combo data. Reeves also have a 2.4-inch OD formation pressure tester which is run through the bit on wireline for realtime pressure evaluation. The TBL method has been tested in a number of semi-vertical wells drilled by Shell, and is ready for commercial use. It saves tripping time, reduces open hole exposure, and is particularly well suited as a low-cost solution for difficult well environments. The next stage is now under development with industry partners. Through Bore Drilling (TBD) uses a drilling assembly with directional drilling and MWD functionality that has a through bore capability to allow tools to be deployed, and other operations to be carried out. TBD is particularly well suited to deviated, horizontal, and extended reach wells where trip-time costs and risks are particularly significant. TBD is an entirely new approach in which the drilling assembly and bit provide more than the drilling function - they are a conduit and a gateway to the borehole and formation. Through this gateway it is possible to perform various operations, including (but not limited to) logging and placement of cement. This can be likened to laparoscopic (keyhole) operations in the medical world, where numerous functions are carried out through a simple conduit brought into place once only. The paper summarises the TBL method and trials to date, and discusses the latest developments around the Through Bore Drilling system.