The Performance of Mud Motors With Two Different Bent Housings

Abstract

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 125858, ’The Performance of Mud Motors With Two Different Bent Housing on Drilling a Lateral Section of Horizontal Wells in North Dakota,’ by Andy Syahputra, SPE, Bill Blaschke, and Jerry Hudson, SPE, Halliburton, originally prepared for the 2009 SPE/IADC Middle East Drilling Technology Conference and Exhibition, Manama, Bahrain, 26-28 October. The paper has not been peer reviewed. Drilling across two sections in a horizontal well in the Middle Bakken formation of North Dakota offers challenges and opportunities for improved well-construction performance. The wells in this area were drilled with three different hole sections after setting the 16-in. conductor at 60 ft. The lesson learned on three offset wells in this area found that a bend setting of 1.15° has contributed to reduce tortuous well paths, controlled dogleg severity, and stayed in a very tight target interval while drilling the lateral section of 10,000 ft along the hole. Introduction Many operators are finding success drilling horizontal wells to develop the Middle Bakken in the Williston basin, which is relatively stable tectonically as compared with other intracratonic sections. The Bakken formation comprises the lower, upper, and middle members. The middle member is the target of the current development and typically consists of silty sand-stone and very-fine-grained sandstone, which is very calcareous and slightly dolomitic in the zones with the best oil and gas shows. The full-length paper focuses on drilling and the performance of mud motors with two different bent housings on three different wells in North Dakota. Discussion The bent housing tilts the axis of the bit relative to the axis of the hole. Significant bit side force is achieved for a relatively small bit offset. This allows the bit to build inclination and/or change the hole direction when the rotary-table topdrive is locked and to drill straight ahead when the drillstring is being rotated. The number of round trips thus is reduced dramatically, provided that the correct bit [polycrystalline-diamond-compact (PDC) bit of six-bladed aggressive designs with durable cutting structure] and bottomhole assembly (BHA) are chosen. The BHA is provided with vibration tools with sufficient weight to be run to the shoe and drill to section total depth (TD) in slide or rotating mode of drilling. The surface-adjustable bent housing allows an incremental adjustment of the bend in the motor from 0 to approximately 3°. This changes the magnitude of the side force generated at the bit while slide drilling and, as such, the achievable build and turn rates. As the bent-housing offset angle is increased, bit side force increases and it becomes more difficult to slide. In the rotary mode, it becomes more difficult to rotate.