While HT wells have always presented drilling challenges, the recent activity increase in the Haynesville shale located across the border between Texas and Louisiana presents a unique and extreme environment for drilling equipment. Not only is there a high frequency of temperature related MWD/LWD failures, the profile and architecture of Haynesville wells has provided an opportunity to study and better understand the thermal behavior of horizontal HT wells in general. Through improved understanding, well specific operational guidelines and planning considerations can be implemented to ultimately reduce the risk of downhole temperature related failures.
This paper discusses a Haynesville horizontal well case study where temperature simulations were compared and calibrated to actual downhole temperature measurements taken while drilling. After calibration of the model was established, a series of simulations were conducted to investigate the sensitivity of bottom hole circulating temperature to choices of drilling systems, fluids systems, mud cooling systems and well design.
The simulation results indicate:
The bottom hole circulating temperature profiles of HT horizontal wells are significantly different than those of vertical wells and can even exceed the bottom hole static temperature.
The simple every day choices made with regards to the drilling program including fluids selection, hole size, bottom hole assembly type, bit hydraulics, and flowrate all influence bottom hole circulating temperature and can either increase it or decrease it.
Optimization in the traditional sense (focused on ROP) does not apply and can result in even higher bottom hole circulating temperatures. The correct procedures are often counter intuitive.
This paper will detail the above mentioned effects on bottom hole circulating temperature and will present optimization guidelines and planning considerations for managing circulating temperatures. At the time of this writing, the implementation of these guidelines and procedures discussed in this paper is just beginning. The overall trends for MWD/LWD performance for the Haynesville, while improving over time still indicate significant room for improvement in planning and operating practices (Appendix - Figure A1). Guidelines and planning considerations, and operating practices for horizontal Haynesville wells are presented along with the reasoning behind them.