Defining Sand Control in an Uncharted Frontier: A Case Study on the Zawtika Field Development in Myanmar

摘要

This paper covers the design, execution, and evaluation of the development of the Zawtika field operated by PTTEPI in Myanmar. This includes the study of the reservoir, the selection of completion methodology, the operational challenges, and the performance of the wells. The Zawtika field development focused on the laminated Plio-Pleistocene reservoirs. The formation comprises a thick sequence of mixed deltaic and shallow marine clastic sediments. A conservative geomechanics study indicated that any reservoirs shallower than 1,700 m true vertical depth (TVD) have high sanding risks and would require an active sand control method. A batch completion campaign was planned and deployed as a mix of single-zone and stacked dual-zone cased-hole gravel packs (CHGP). A pre-gravel pack acid treatment was tailored for formations with high chlorite content and fines stabilization. A fracture- and gravel-pack service was the primary gravel pack option followed by high-rate water pack (HRWP) depending on water zone proximity or a lack of stress barrier. The sanction that was placed on the country at the startup of this campaign and the limited infrastructure in place led to various challenges during different stages of the campaign. Over 15 months, 17 wells were completed on three platforms with eight single-zone wells and nine stacked dual-zone wells. This totaled 26 zones where 10 zones were completed with the fracture- and gravel-pack service and 16 zones with HRWP. These jobs were executed on a tender assist for the first platform and on a hydraulic workover unit for the following two platforms. These were among the notable points for the campaign: 1. First CHGP completion in Myanmar, 2. Achieved production objective with zero sand production, 3. Introduced the technique of pumping HRWP in sweep stages for longer intervals in Myanmar, 4. Introduced several fluid systems in Myanmar, including a polymer-free carrier fluid, acid system with diverting agent, fluid loss pill, and clay stabilizer, 5. Completed all wells without downtime related to delivery of products despite the remote location and logistics between multiple countries, 6. Completed the campaign without any HSE incident and with high operating efficiency.