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Technical Paper: Successful Implementation of Engineered Fiber Based Loss Circulation Control Solution to Effectively Cure Losses While Drilling, Cementing and Work Over Operations in Oman

Society: SPE
Paper Number: 166529
Presentation Date: 2013
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Abstract

Oman is a hotspot for drilling activity and wells are being drilled in different environments, varying from deep exploration and development for gas and oil to water injection/disposal. One challenge tops all other challenges: Lost Circulation. Due to the fractured/fissured nature of the formation and low existing reservoir pressures, all major operators are suffering from lost circulation challenges. Some of the challenges are mud losses while drilling leading to cost overruns and HSE concerns, primary cement job failure due to not getting the cement up to the desired height resulting in subsequent sustained casing pressure and corrosion, inability to perform workover activity on certain wells due to losses. Enormous quantities of water are required to maintain well control and due to the limited availability of water throughout Oman, this becomes another critical issue. An engineered-fiber-based lost circulation pill has proved successful for addressing these challenges in multiple fields for Petroleum Development Oman.

Drilling shallow wells in Oman through the naturally fractured limestone formation of Natih usually results in significant losses of up to 55 m3/h [346 bbl/h] even with a low-density drilling fluid of 1,033 to 1,070 kg/m3 [8.6 to 8.9 lbm/galUS]. Packoffs are often observed due to the swelling shale section, which leads to several attempts with kickoff plugs and sidetracking. Engineered-fiber pills enabled total returns to surface when no previous lost circulation solution had worked. This also enabled cement to be brought all the way to surface using 1,410 kg/m3 [11.8 lbm/galUS].

In another field, a workover rig was mobilized to perform a well kill operation and pullout. Due to total losses through perforations into the reservoir, the well kill could not be completed. In addition, every time the water level fell, gas started to flow in the well. After 17 attempts and 8 lost circulation material pills, a total of 763 m3 [4,800 bbl] of well-supply water had been pumped. An engineered-fiber pill at 1,474 kg/m3 [12.3 lbm/galUS] was designed and bullheaded into the perforations. The pressures while pumping and squeezing rose to 11,031 kPa [1,600 psi]. The well was shut and observed for three hours without any pressure increase, indicating losses were cured and gas flow had stopped.

Engineered fibers have proved their value in a range of lost circulation applications in North Oman. These pills have been successfully used to mitigate losses while drilling, while cementing, during mud circulation before a cement job when the casing is on bottom, and in workover jobs in depleted reservoirs. With the level of success achieved with such treatments, in some fields it has become a standard practice for curing losses.

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