Recent Advances In Horizontal Drilling

Abstract

Abstract This paper describes recent advances in horizontal drilling technology including multibrach wells, geosteering, advanced drilling bits and motors; new short-radius tools, and small diameter drilling systems. Multibranch horizontal wells can reduce horizontal drilling costs by 20 to 30 % and the size and number of offshore platform by up to 50%. Geosteering systems utilize logging-while-drilling tools to accurately guide horizontal wells to avoide obstacles and gas water contacts and to significantly increase horizontal well productivity. Improved PDC and TSP bits and new high-power motors have potential wells. New short-radius motor systems 12 to 30 m (40 to 100 ft) radii allow 305 to 457 m (1000 to 1,500 ft) horizontal wells to be drilled more rapidly. Advantages of short-radius wells includesidetracking wells below gas caps or troublesome shales,intersecting fractures close to vertical wellboressignificantly reducing the length of the build sectionreducing drilling time and cost andallowing pumps to be placed lower in the wells New small diameter systems allow 92 mm (3 5/8 in) single and multibranch horizontal wells to be sidetracked from 114 mm (4 ?) casing Implementation of these new technologies should significantly increase the use of horizontal wellsworld wide. Multibranch Wells One of the most important developments with horizontal drilling is the increased use of multibranch wells. Figure 1 shows a Soviet (1) multibranch well with ten lateral. This well was drilled in the 1950's with nurbodrills. The laterals produced a 17-fold increase in oil production in this well. Figure 2 shows a Soviet dual branch well drilled in the Macova field in 1968. This well cast 1.23 times more than a conventional well and produced 10.5 times more useful length in the pay zone. By 1975, the Soviets had drilled over 30 multibranch and horizontal wells(2). They typically drilled vertical well just above the pay zone and then used turbodrills or electrodrills to drill five or six stand or horizontal branches 61 to 305 m (200 to 1,000 ft) into the pay zone. These multibranch wells cost 30 to 80% more han vertical wells, but produced up to 17 times more oil or gas. From 1953 to 1980, the Soviets had drilled over 30 multibranch and horizontal well2. Including:57 development36 exploratory8 relief wells10 injection wells A total 329 slant and horizontal branches were drilled in these wells with an accumulated pay-zone penetration of 175,260 m (575,000 ft.). This included 2120 sharply curved brances sidetracked from open holes (i. e. no cement plugs) with a total extension of 21,336 m (70,000 ft). Build rates up to 10 °/30 m (10 °/100 ft). Build rates up to horizontal branches were drilled with a maximum length of 640 m (2,100 ft) and a total length o 4,724 m (15,500) ft). Petro-Huun 3 used a dual branch well to drain an entire Austin Chalk lease as shown in Figures 3 and 4.