Fit for Purpose Low-Cost Solution for Upper Drain Accessibility in Dual Wells
Authors: Saqib T. , Mirza O. T. , Sabri A. M. , Al-Hajri S. S. , Mefleh I. R. , Butler B. 
Published: October 2023

Located in the Arabian Gulf, approximately 135 km north-west of Abu Dhabi, this giant mature heterogeneous carbonate field is one of the largest fields in the world. The field is characterized by a number of multi-stacked heterogeneous reservoirs. With oil recoveries ranging from 3% to 45%, a large gas cap, and reservoir heterogeneities affecting production performance, the field faces challenges related to advanced maturity. The initial phase of development occurred under natural depletion from 1962 to 1973, and then the development strategy was changed to peripheral water injection, followed by Crestal gas injection in 1994. As a result of the movement of gas and water, the life of the wells has been affected. Because the saline pressure is approximately 1,100 psi, as soon as the well is hit by water, it cannot flow.

As a key to meeting the production target for the upcoming projects, improvements in reservoir optimization through advanced well architecture are being considered to achieve the production target for this project, as well as ways to have dual wellbore accessibility, thus reducing the number of wells necessary. Having the ability to access lower completion levels and stimulate them is an essential part of the process. Utilizing technology to increase the accuracy of well placement will be a key factor in optimizing the well architecture. Additionally, optimization of well trajectories is also necessary to ensure that the reservoirs are being accessed efficiently and to maximize production. The use of advanced completion technologies can ensure that the wells are properly stimulated.

Advanced multilateral completion technology is used to access laterals within the well. In order to minimize the number of wells and associated surface facilities, including platforms, the wells will target multiple reservoirs with two separate laterals.

The first MultiLateral TieBack System (MLTBS) was successfully piloted in 2014 and was a great success [1]. It featured a cemented junction with an intermediate lateral liner, which was then completed to Level 5. Optimum cost and duration of the well was required in order to achieve these objectives without compromising on any of the objectives. This study was done in order to come up with a better and more cost effective solution for accessing the upper drain while ensuring segregated flow through independent strings and maintaining well integrity and safety as primary objectives. In order to fulfill the accessibility and control requirements, it was necessary to utilize a Dual Bore Deflector & Latch Coupling as part of the completion of the MLTBS. In this new design however, the intermediate cemented lateral liner was removed, and instead the production tubing would tie back into a lateral completion in the open hole.

This new well design using the MLTBS equipment with an open hole lateral completion was selected for its advantages over the previous cemented junction design: Low CAPEX for Equipment: Saving of additional equipment for upper lateral like packer & assemblies.Low CAPEX for Operations: Rig-time saving in for cementation, clean out, milling of transition joint and running and setting the permanent packer in upper lateral.

Some of the reservoirs weren't developed at first and were grouped as Undeveloped Reservoirs (UDR), and their development strategy is mainly based on line-drive development. In this type of completion, the ICDs will be used for water injector wells for line drive systems and producers, allowing control of the undesired fluid flowing through the ICDs by manipulating them in the lower completions.