Abstract
One of the limiting parameters while drilling deep extended reach (ERD) wells with 6-in. and less open hole diameter is a downhole temperature (DHT). In such small diameters a temperature can easily reach the limit of existing measure while drilling (MWD) and logging while drilling (LWD) tools and restrict the application of them. The manuscript studies main factors affecting DHT in slimehole application and the ways to manage it, as well as field application of obtained results.
The study of DHT while drilling slime ERD wells started with comprehensive analysis of main sources of heat generation, their contribution to DHT as well as temperature transmission along the borehole. The main sources and factors (as geology, well design and profile, BHA and drill string design, drilling fluid type and design, the drilling practices, ROP, friction factors etc.) were ranked by its impact, followed by the development of the model which could simulate their contribution. Based on the model the prevention and mitigation measures were developed to keep DHT within desired limit during a well construction process.
The study was implemented while drilling slime ERD wells in the fields (Middle East) with static reservoir temperature of 250 - 260 deg F. All the modeling results were confirmed with actual field data proving the validity of the simulations. It was confirmed as well that the downhole temperature management in slimehole application is more complex due to many limiting factors, when main of them are coming either from rock properties, like fracture gradient or downhole tools (for example both are limiting the flow rate which found to be the key player in DHT management).
It was shown that even with all developed measures to maintain DHT in slime wells the limit can be reached in deeper wells, due to limits of the downhole tools available in the industry.
The manuscript describes an approach to do the engineering study of one of the main limiting factors which can prevent drilling of deep ERD wells.
