Optimized Drilling Techniques Significantly Decrease Drilling Time - East Apache Field
Authors: Yacone Frank A. 
Published: December 2007

This paper describes the optimized drilling techniques used to decrease significantly the drilling time for a 20,000 ft (6096 m) Springer sand well in the Anadarko basin of Oklahoma. Use of these drilling parameters greatly increased the penetration rate and maintained excellent hole stability. With these results, the well was drilled quicker and at less expense than anticipated.

Introduction
The Anadarko basin is one of the most complex and challenging deep drilling areas in the world. In the East Apache (Springer sand) field, much difficulty was encountered in the drilling of the discovery well and three development wells in the field. On the average, these wells required more than 300 days to reach the final casing point. In the drilling of the Fort Sill Unit 2 Well 1 (the subject of this paper), the previously drilled wells were researched thoroughly, previously drilled wells were researched thoroughly, and from these findings evolved the optimized drilling techniques used. It was found that the maximum recommended revolutions per minute and weight on bit (WOB) could not be applied without hole deviation becoming a problem. To alleviate this problem, a three-point stabilization system was used problem, a three-point stabilization system was used in conjunction with tandem square drill collars. Also encountered were sloughing shales in the Atoka and Morrow zones. This problem was solved by using an invert-emulsion mud which had no effect on the hydratable clays in the shales. The last problem was low penetration rates. The wells previously drilled averaged between 1 to 2 ft/hr (0.305 to 0.61 m/hr) below 17,000 ft (5182 m). By using the previously cited parameters and by optimizing the hydraulics program, mud cleaning, and jet selection, the program, mud cleaning, and jet selection, the penetration rate was increased to an average of 4.83 penetration rate was increased to an average of 4.83 ft/hr (1.47 m/hr) below 17,000 ft (5182 m). This provided a saving in drilling time of 112 days when provided a saving in drilling time of 112 days when compared with the average of the best three wells drilled.

Research of Previously Drilled Wells in the East Apache Field
The East Apache field was discovered with the drilling of the Richard Vail No. 1 in 1971. This well was drilled 20,889 ft (6400 m), took a gas kick, and stuck the drillpipe. Fishing operations commenced, but the well could not be cleaned out and had to be abandoned. Three offset wells to the Vail No. 1 have been drilled, with two being producers and one a dry hole. The producers are the A.O. Belcher No. 1 and the Fort Sill Unit 4 Well 1, while the dry hole was the Fort Sill Unit 8 Well 1. A plat of the field is shown in Fig. 1.

Sloughing Shales
The East Apache field wells were drilled with freshwater mud using mud weights and casing setting depths as seen in Fig. 2. Sloughing shale problems were not severe until the Atoka formation was penetrated at approximately 13,400 ft (4084 m). penetrated at approximately 13,400 ft (4084 m). Freshwater filtrate from the mud adsorbed onto the shales, causing the water molecules to become "captured" and hydration to take place.
JPT
P. 1877