Extended Reach Stimulation with Coiled Tubing: A Case Study

Abstract

Abstract Extended reach horizontal wells in Western Canada and around the world are increasing in numbers as operators maximize well production. As the length of the horizontal increases, so does the challenge of open hole stimulation. Burlington Resources, in association with BJ Services completed what is believed to be the deepest open hole horizontal re-entry with coiled tubing, in the world. This paper reviews stages of planning, design/modelling and operations required to successfully stimulate the Burlington Hinton well with coiled tubing. The well was completed to a total depth of 21,670 ft with end of tubing at 18,308 ft. The 3,363 ft open hole section was drilled with a 5.875 inch bit. A 1.75 inch tapered coiled tubing string was designed to reach total depth (TD) unassisted by any extended reach bottom hole assembly. Several different factors, including completion and coil size, dogleg severity, buoyancy, friction, fluid type and others affect possible lateral extension into the open hole. Some of these factors can be identified and configured prior to running coiled tubing in hole. Others change during treatment. A computer model, Circa, was used to design the coiled tubing string size and to predict effects of many variables. Once the process for entering the well was designed, three other methods were contemplated during the operational stage to assist the coiled tubing to bottom. Invert mud was left in the open hole in order to lubricate the coil and reduce frictional drag.A metal to metal friction reducer was on location as a contingency to reduce friction in the system.The coil could be displaced to nitrogen and "floated" in. Only the first of the above procedures was required to reach TD. A detailed pumping schedule during run in hole was designed to keep the invert mud in hole until reaching TD. It was then removed prior to pumping acid. This paper references some of the fluid compatibility issues associated with pumping water, diesel, and acid when in contact with drilling mud. With appropriate planning, design/modelling and execution, this case study proves that a successful treatment program can be performed on extended reach horizontal wells.