Slant Hole Drilling-- Offshore Peru
Authors: Storm James C. 
Published: December 2007

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc.
Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.
The discovery of oil production at a very shallow depth off the northern coast of Peru, presented a rather interesting situation to the presented a rather interesting situation to the operator, Belco Petroleum Corporation. The problem was not only, in drilling, but also in problem was not only, in drilling, but also in servicing and producing the wells economically. The shallow depth and low pressures made it necessary to plan for some method of artificial lift early in the life of each well. The use of a true vertical depth of from less than five hundred feet to two thousand feet limited the number of wells which could be drilled from one jacket by conventional directional methods to four, and then only by building angle at very high rates. The shallow depth of the field would have made it necessary to set numerous small structures and this would have created additional problems and expense in laying many flow lines and maintaining more aids to navigation. The size of these structures was inadequate to accommodate producing and servicing equipment which would have made the continuous use of an expensive mobile service unit necessary.
Working with Belco Petroleum Corporation, new approach was devised which would utilize a rig capable of spudding the wells at an angle rather than vertical. A rig was built, called a "Tilt Rig" on which a patent is now pending, capable of spudding and operating from vertical through a range of angles to a maximum of thirty degrees. Following a test run, the rig was packaged and shipped to Talara, Peru, where it was packaged and shipped to Talara, Peru, where it was installed on an offshore platform designed and built specifically for its use.
The rig consists of conventional equipment modified and adapted to this special application. Since the depth requirements were so low it was possible to use a single skid on which were possible to use a single skid on which were mounted the derrick, rotary, drawworks, and power supply. The derrick was constructed with power supply. The derrick was constructed with two guide channels extending from the base to the crown so that all traveling equipment would be confined in its movement and travel on rollers when the derrick was in a tilted position.
The rotary table was mounted so that it could be tilted at the same angle as the derrick with its center remaining in line with the line of travel of the equipment in the derrick. An electric pump was installed to insure ample lubrication of the rotary when operating at high tilt angles. No special lubrication was required for the swivel. Due to the shallow depths being drilled, it was decided that laying down the pipe on trips would be desirable and a hydraulic pipe handling device was built which simplified this operation. A conventional racking arrangement could be made if it is found to be desirable during deeper drilling.