High-Pressure Jet Kerf Drilling Shows Significant Potential To Increase ROP

Abstract

Abstract The most effective approach to reduce the cost of drilling oil and gas wells is to increase penetration rates. Researchers have investigated means to drill rock faster for many years, and jet-assisted drilling is one approach that has been considered various times. While incorporating various jetting techniques into the drilling process has been found to be effective in increasing penetration rates, problems with leaks, system reliability, and high costs have prevented widespread application of high-pressure (HP) jetting technology. An R&D project[1] sponsored by the U.S. Department of Energy was undertaken to develop and field test a HP drilling system based on employing specially designed jet bits to erode radial kerfs (grooves) in the rock which are then broken off by the mechanical cutters. Tools required for jet kerf drilling (JKD) were successfully developed and tested in the laboratory and field. This project's original concept was to employ coiled tubing (CT) to convey the BHA into the well. Later in the effort, rotary drilling with jointed pipe was also investigated and successfully implemented using an upgraded conventional rig and commercial double-shouldered drill pipe. Project highlights include development and testing of HP motors and jet kerfing bits, a field test using a CT-based drilling system, and a second field test using conventional rotary drilling equipment. Based on these successes, JKD is now highlighted as a technology that has potential to increase penetration rates while remaining reliable and economic. Implementation of JKD tools and techniques within the USA gas and oil industry is now feasible. However, it will not be a simple process, with the current business environment remaining the most challenging hurdle. Successful implementation will require close cooperation from drilling contractors, operators, and bit manufacturers. Introduction The oil and gas drilling industries have always sought to develop technologies that drill rock faster. There are substantial economic benefits to be gained by increasing the rate of rock removal and hole construction. Drilling faster reduces overall field time, which directly translates into reduced costs for producing oil and gas resources. Economic studies of oil and gas wells have repeatedly documented that drilling efficiency is a major factor in the overall economics of gas and oil exploitation. Figure 1 presents the time breakdown for drilling a group of wells from a survey study[2] conducted by MTI and sponsored by Gas Technology Institute (GTI). These data, representing 3111 wells, show that one-third of the time to construct a well was spent drilling. This is the single largest component in the entire process of well construction. When data from only deeper wells are considered, the percentage of time spent drilling was even higher—almost 50%. Therefore, to reduce well construction costs substantially, drilling time must be reduced. Major reductions of time spent in other activities or categories would not have an overall impact as significant as reducing drilling time. Several approaches can be considered for reducing total drilling time; however, the most effective way is to improve drilling efficiency. Moreover, an increase in rate of penetration (ROP) must be accompanied by equal (or greater) equipment reliability so that overall trip time is maintained. Because benefits from modest increases in ROP are quickly offset by increased equipment costs or extra trip time, it is easy to demonstrate that significant increases in drilling rate (100% and more) are necessary for a significant overall impact on well costs.