In 2011, ADCO embarked on a project of well abandonment in Town field, Located in an urban area approximately 25 km South-East of the main island of Abu Dhabi. Each of the three wells presented individual technical challenges and, due to proximity of the populated areas, complexities with logistics and emergency response planning arose. As well as significant presence of toxic H2S in the Town field reservoirs this categorizes those wells as critical high profile wells. And this necessitated extensive engagement with ADCO coordinating with external authorities of concerned parties' throughout the project.

Today, well durations are relatively longer due to several factors. Some of these include but not limited to intermediate section down hole losses. Therefore, there is an opportunity to explore possible ways to reduce well duration and cost while meeting all business objectives with 100% HSE. Dammam, U.E.R, and Simsima are karsts-prone carbonate aquifers widely developed across UAE. As formation pressures are depleted, severe to total losses is increasingly occurred during drilling through these shallow aquifers. Conventional loss curing agents are often failed, especially in Simsima, because of their inability to set in such complex and large fractures and caverns. ZND gel is a water-soluble high molecular polymer, which will automatically set and seal the space after being pumped into loss channels. As hardly be diluted by any formation fluid, a gel slug is formed to isolate drilling fluids and consolidate agent from being washed away into loss zones. In this study, we present a composite solution of ZND gel and Cement applied in onshore Abu Dhabi, which effectively mitigated the total losses encountered in Simsima.

The purpose of this paper is to share the results and knowledge learned in implementing new procedure and techniques to rotate the 5-1/2", 26 PPF, T-95/P-110 Frac String (FS) during running into Unconventional wells. Developed by ADNOC Onshore ASR - UC Drilling Department at Abu Dhabi (U.A.E.) the novelty involves six (06) different technologies necessary to minimize axial buckling in the monobore completion while maximizing well accessibility and integrity during the Rigless frac operations. The 6 key enablers technologies employed to rotate the Frac String up to 30,000 pound-ft: Connection: strength to withstand rotation required to release the axial buckling.High Speed Reamer Shoe: open hole debris cleaning / obstruction removal.Bonded Ceramic Centralizers: providing 80% standoff, reducing the friction factor and removing the mud cake with the rotation.Casing Running Tool: designed to wash down and rotate FS during running.Rotating Tubing Hanger: enabling FS rotation using different techniques and design a new mechanism for it after landed and locked into the Tubing Head Spool.Rotating Cement Head: ability to rotate the FS while pumping cement and plugs simultaneously. Because of friction, sliding during running will result in helicoidal buckling of the FS that has a negative knock down effect on later completion operations / interventions and even in some cases not possible to reach the TD. The results of previous UC wells where FS was run in sliding mode revealed issues due to the helicoidal buckling of the FS impairing annulus / cement bond quality, creating tortuosity and altering the Internal Diameter (ID) leading to issues in accessing the well bore with the Plug and Perf tool for the fracking operations. The total depth for standard UC wells ranges from 16,000’ to 23,000’ MD with ± 12,500’ TVD and ± 8000’ MD 8"1/2 horizontal section dipping up to ±92° inclination for production reasons. Such profiles generate Friction Factor (FF) ± 0.5 in Open Hole. Based on performed simulations and depending on the well profile, surface torque required to rotate the string was between 25,000 to 30,000 pound-ft. This paper will describe and provide details on how the FS helicoidal buckling was minimized and its limitations overcome thanks to the six key enablers technologies devised by Onshore ASR - UC Drilling Department. It will also highlight other important added benefits such as mud cake removal, improved annulus geometry and cement bond.