To ensure safe operations and to maximize well potential, PTTEPI has formulated a sand production management strategy to reduce risks due to sand production while extracting natural gas resources from the young clastic reservoirs formed during Plio-Pleistocene geological sequence. Over the 2 years of historical production, the strategy has been fine-tuned and enhanced to improve its effectiveness in managing sand production. The strategy integrates efforts from both subsurface and surface disciplines. It covers initial well completion design to address the need for sand control, continuous recording and analysis of performance data after a well is put on production to monitor and manage sand production within acceptable limits, data acquisition programs to obtain additional information for analysis of sand production, and remedial and mitigation initiatives to address sand production. The following sections will discuss, in more detail, each component of the sand production management strategy.

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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: First CHGP completion in MyanmarAchieved production objective with zero sand productionIntroduced the technique of pumping HRWP in sweep stages for longer intervals in MyanmarIntroduced several fluid systems in Myanmar, including a polymer-free carrier fluid, acid system with diverting agent, fluid loss pill, and clay stabilizerCompleted all wells without downtime related to delivery of products despite the remote location and logistics between multiple countriesCompleted the campaign without any HSE incident and with high operating efficiency

Sand and fines production in oil and gas wells are a major challenge that can result in production system failures. In unconsolidated sand reservoirs, proper sand-control practices are necessary to help prevent reservoir sand production. To remove formation damage and control fines migration, acid treatments are pumped ahead of sand-control treatments, which can be challenging because variations in mineralogy determine fluid performance and require a customized fluid selection. For this case, improvements in cased hole sand-control completions were initially sought by switching to high-rate water pack (HRWP) or fracture for placement of gravel (FPG) techniques; however, obtaining fracture conductivity and minimizing out-of-zone fracture growth was challenging. To accomplish the latter, fluid selection was optimized with linear-gel systems and relative permeability modifiers as prepad systems. Operators should know the formation's composition at the treatment point for a successful acidizing treatment to be performed. The dominant mineral component and temperature of the target formation determines the most effective preflush, hydrofluoric (HF)/hydrochloric (HCl) acid treatment blend, and preflush/treatment volume. The successful implementation of HRWP and FPG techniques produced excellent results with regards to skin minimization and production maximization. The HRWP technique was applied when gas/water contact was nearby, allowing flow from a moderate to high payzone kh (permeability × net pay), and FPG was used to produce a proper flow in low kh formations. The goal of sandstone-matrix acidizing is to remove siliceous microparticles blocking or bridging pore throats by injecting acid formulations containing HF acid. The presence of potassium feldspars, sodium feldspars, illite, and zeolites is a concern because these compounds can form or contribute to forming significant matrix-blocking precipitates, such as sodium or potassium fluosilicates and aluminum fluorides, during HF/HCl treatments. Variations in mineralogy determine fluid performance and make customized fluid selection necessary. The goal is to minimize the risk of over acidizing the near-wellbore region and to extend the reaction for deeper penetration when possible. In some cases, the acid systems with the equivalent strength of up to 1.5% HF acid were used. This paper describes the planning process, acid treatment selection based on laboratory testing, placement and diversion techniques, sand-control completions selection, operation summary, and evaluation of treatment success.