HZ Marcellus Well Cementing in Appalachia

Abstract

Abstract It has become a high priority task of the drilling engineer to be closely involved in all aspects of the cement job design for a horizontal Marcellus well. Close cooperation with the cementing service company is required. It should be common place to use a simulator to facilitate job design and predict situations which could result in job failure. Comparing simulator runs to real time monitoring of job parameters can give indications of down-hole problems. Making on the spot decisions to change the job design can sometimes lessen or prevent the negative impact on the job performance which would have resulted if no changes were implemented. This paper will review the accepted industry standards for hole conditioning, pipe centralization, pipe movement and slurry designs for HZ wellbores. A chart will be presented that includes all the tasks required for job design. Illustrations are provided to give operators realistic expectations of the engineering support they should be getting from their cementing service companies. Several slurry designs being used in Appalachia are presented and the required properties needed for successful horizontal well cementing in Appalachia. Results of these slurry designs will be presented as a relationship to the breakdown and treating pressures during the subsequent hydraulic fracturing treatments. The issue of the prevention of backside gas pressure will be discussed. Introduction Recent negative publicity about the well construction procedures for Marcellus wells has increased Appalachian operators' attention to cement job designs. A focused and systematic approach using accepted industry best practices can eliminate the reoccurrence of such problems. HZ Marcellus well construction has ushered in a new era of well cementing into the Appalachian Basin. In the past, well construction usually meant an air drilled vertical well less than 6,000' MD with a BHT of +/- 120F into an under pressured reservoir. Today's HZ Marcellus wells are fluid drilled, with a BHT of 140F to 160F, a MD +/- 13,000 ft and TVD of +/- 7,000 ft. Pore pressure gradients in the Marcellus can be > 0.6 psi/ft of TVD. Getting a good cement job can be hindered by fractures and faults, doglegs, washouts, cuttings and hole cavings. Best Practices All of the same practices developed for cementing vertical wells will also apply to horizontal wells. The difference being that horizontal well cementing requires the understanding that the slurry is being placed in the annulus of the horizontal lateral and also in the vertical annulus. Table 1 below was taken from the work by Gai, et.al. about cementing horizontal laterals being drilled in the Wytch Farm Field in the UK Sector of the North Sea. At the time in the early 1990's these wells with 1300 M laterals at 1600 M TVD were world-record breaking extended reach wells. Today, cementing HZ Marcellus wells, we can use these same parameters checklist when designing the HZ cement jobs. It is however, necessary to be cognizant of the differences between the well/reservoir conditions in the North Sea and the Appalachian Basin. We can use Table 1 as the blueprint for the design of the completion cement job on a HZ Marcellus well. The following conditions are for a typical HZ Marcellus well in northeastern quadrant of Pennsylvania. Similar conditions exist elsewhere in the Appalachian Basin with slight changes as the result of depth variations.