Discovered in 1957, Manifa field is a giant offshore field with six oil-bearing reservoirs that cover more than 800 km2 in the shallow waters northeast of Saudi Arabia. Typical wells in this field extend over 20,000 ft with more than two-thirds being considered extreme, extended reach wells that run beyond 24,000 ft. The longest high angle well in Saudi Arabia, 32,000 ft total depth (TD), is in this field.
Coiled tubing (CT) is a well-proven method to access these long, horizontal wells and is used frequently in the completion to perform matrix stimulation. However, it faces certain limitations that can prevent it from accessing the full TD in these extended reach wells. Reach capabilities depend on the size of the reel, the diameter of the coil, the material of the coil, the completion size and the wellbore geometry, to name a few. In order to extend the reach length of CT, hydraulic tractors in various sizes have successfully been run to pull the CT to TD in Manifa field. The CT tractor eliminates the aforementioned limitations by pulling the CT with forces of up to 4,000 lbs and removing the issues relating to helical buckling.
The benefits of extending the lateral reach capacity for the CT are multiple. Since the wells have already been drilled, there is the sunk cost associated to the depth of the well. If there is no method to get the CT to this depth, this cost cannot be capitalized on. Additional sunk costs are incurred by preparing, transporting and mixing all the stimulation fluids required to complete the entire well to the job site. If the CT hangs up far shorter than TD, these costs are again not recouped. Further, by not stimulating the well from the toe, or TD, the total production potential of the well is unrealized. In one of the wells, a world record was achieved when the CT tractor reached 28,759 ft. The operator wanted to access the open hole for stimulation, but without the 2 ½” CT tractor, the 2” CT would only have reached ~ 85% of the open hole section, leaving ~ 15% of the reservoir unstimulated. In another well, the CT tractor extended the reach of the CT by 5,610 ft, or 28%.
The CT tractor has proved itself capable of increasing the length of CT used on Manifa wells. This not only increases the operator’s return on sunk costs but more importantly, it increases the potential for full reservoir stimulation and boosts the productivity index significantly.
This paper documents the activity and successes that CT tractors have brought to Saudi Aramco in Manifa field.