Step Change in CTD Strategy of Multilateral Drilling Using Under-Balanced Coiled Tubing Drilling UBCTD Technique in an Onshore Sour Gas Field-UAE -Case Study
Authors: Osama Mohamed , Sumaida Ali Sulaiman Bin , Shamlan Abdulla Bin , Shahat Ayman El , Mutawa Ahmed Al , Almazrouei Saeed , Saleh Abdalla , Yousfi Fawad Zain , Almteiri Nama Ali , Baslaib Mohamed , Deshmukh Rohit V. , Solaiman Tarek , Abdulsallam Fouad , Mantilla Alfonso , Ladmia Abdelhak 
Published: April 2024

Abstract
The Oil and gas industry needs to adapt its business models to meet the growing energy demands and to use our resources efficiently and responsibly for the benefit of humanity worldwide. The United Arab Emirates aims to produce enough gas to meet its own needs by 2030. To do this, the country has started several projects to explore and assess potential gas sources. This study focuses on one of these projects, which involves drilling three wells in an onshore field using a coiled tubing (CT) underbalanced drilling (UBD) technique to access gas from tight reservoirs.
The Under Balanced Coiled Tubing Drilling (UBCTD) technology has a globally proven record of enhancing the production rate compared with conventional overbalanced techniques.
The lateral length is limited due to buckling and lock-up of the coiled-tubing string, hence the multilateral drilling can overcome this limit and increase the well drainage compared to long horizontal sections. Implementing Coiled Tubing Drilling (CTD) with Multi-Lateral overcomes CTD limitation need for a single extended reach horizontal hole as conventional drilling, due CT lower Buckling limit, thus shorter lockup depth and reach in comparison with Conventional Horizontal Section.
Detailed planning was carried out for the technology implementation and there were many challenges in the operations, nevertheless, this is the first project of it is kind for the operator company The lessons gained from daily challenging operations are considered the steppingstones for the technology implementation in Abu Dhabi.
Comprehensive planning and simulations were done to overcome the challenge of different reservoir pressures, wellbore instability, and the absence of side-track operations history with CTD.
The technique for multilateral drilling is characterized according to definitions established in 1997 during the Technology Advancement of Multilaterals (TAML) Forum held in Aberdeen. These standards classify junctions as TAML Level 1, 2, 3, 4, 5, or 6 based on mechanical complexity, connectivity, and hydraulic isolation. In UBCTD wells, the most common multilateral technology is with TAML level 1, which is done by open-hole sidetracks with barefoot completion.
CTD drilling in multiple directions was effective, and one well finished with UBCTD had gas production rates about two to three times higher than conventional wells.
The UBCTD pilot was very fruitful in all viewpoints contrasted with the pre-set achievement factors as coordinated by the practicality concentrated on that characterizes the accompanying achievement measures Adhere to Healthy Safety and Environmental Considerations. Drill 4000 ft using CTD.Drill the well laterals completely underbalanced.Achieve a 1.6-2 times production increase compared to Conventional Well Gas Production.
This paper will highlight the project difficulties and lessons learned from coiled tubing drilling (CTD) in all the wells that were drilled and focus on a multi-lateral strategy to achieve the project goals.