First Worldwide Coiled Tubing Stimulation of a Quad-Lateral Extended Reach Power Water Injector Using Multi-Lateral Tool With Gamma Ray & Distributed Temperature Survey
Authors: Jassem H. , Al-Shehri Ayedh M , Al-Shammari Nayef S. , Al-Gamber S. D. , Mutairi K. M. , Said R. , Barkat S. , Ahmed D. 
Published: February 2017

The study well was first drilled as single lateral Power Water Injector (PWI), then sidetracked as a multilateral injector with a total reservoir contact of 23,094 ft. The well was completed with three new laterals all placed up-dip in the water leg. This geometry was specifically intended to increase injection potential and provide more pressure support in the lower transmissibility areas of the well's complex, carbonate field.

This paper discusses the Coiled Tubing (CT) accessibility challenges, technology deployment and lesson learned for stimulating the first quad-lateral extended reach PWI ever drilled in the study area in Saudi Arabia. The PWI is used to increase the injection capacity and provide extra support to reservoir pressure.

Due to the challenging extended reach well trajectory, technology unavailability, challenge of effectively access all 4 laterals and properly identify each later to stimulate them, CT with real time downhole monitoring was used in conjunction with a multi-lateral tool access. The multi-lateral tool (MLT) was used to provide controlled, oriented mapping to access each lateral independently. The indication for the correct lateral was confirmed by both downhole pressure drop across the multi-lateral tool. As all the laterals are extended reach, getting to total depth (TD) was challenging for some of the laterals even after implementing all the reach techniques. In order to be efficient and identify which lateral was accessed an innovative method was developed by using Gamma Ray (GR) tool and casing collar locator (CCL) to properly identify each lateral before having to reach TD to determine the lateral accessed.

Once the proper lateral is accessed and determined, the acid treatment placement was pinpointed to and optimized by distributed temperature survey (DTS), which helped determine in real-time high permeable thief zones and tight or damaged zones. The treatment schedule was designed to divert from high intake zones using viscoelastic surfactant diverting acid system, followed by hydrochloric (HCl) acid for stimulation. The intervention was completed successfully without any safety incidents. The use of GR, CCL and downhole pressure & temperature measurements in conjunction with MLT tool gave the ideal method for lateral access and lateral confirmation especially when reaching to Total Depth (TD) was not feasible due to CT lockup. In addition the use of DTS for optimum stimulation placement was the key in improving operation efficiency.

The methods developed in this paper on how downhole measurements such as pressure inside and outside CT and it's differential, CCL, GR, MLT and DTS can be used in Multilateral wells has proven to be a major success. This first intervention of its kind has opened new innovative ways and techniques of confidently stimulate all the multilateral extended reach wells in Saudi Arabia.