Implementation of Multistack Sand Exclusion Methodology in Extremely Unconsolidated Wells: Learnings from Marginal Daman Field, Western Offshore India
Authors: Patil Ravindra M , Murthy P V , Bhatia Kutbuddin , Deshpande Mayur , Pande Karan 
Published: March 2021

Abstract
The Daman marginal field is a prolific gas-producing clastic field with highly unconsolidated Paleo-Miocene sandstone formations and a wide variety of lithologies across multistack sand layers. As such, high-rate water packs (HRWPs) are the ideal completion method in many Mumbai fields. Because multistack reservoirs require good zonal isolation, and to prevent crossflow between reservoirs with different pressure regimes, multistack sand exclusion (MSSE) methodology was selected for primary well completions with minimum rig time and a high degree of treatment placement accuracy. From an operational standpoint, exploiting these layers using this method means more control points can be achieved across these heterogeneous layers, and the MSSE completion is ideal for multiple applications in a shorter period, helping sustain sand-circumscribed gas production from these unconsolidated layers.
During the design phase, grain-size distributions and core study defined the sand range from generally clean, coarse, and sorted to poorly sorted, with high-fines content and clay rich. To address the unique challenges of deep offshore operations, formation technical difficulties, high-stakes economics, and the significant untapped potential from these Daman sands, the MSSE approach was designed and implemented in this field. Historically, for multistack wells, an HRWP is performed zone by zone whereby the process of sump packer installation, perforation run, deburr run, screen assembly installation, and pumping is repeated for each zone. In Well A, the MSSE system was applied without any repetition and all in one phase. All layers were perforated and positively isolated. Each interval was individually opened for the HRWP treatment using a low-friction low-residue carrier fluid. Using a high-packing-factor proppant at a higher rate, the well was treated sequentially from the bottom of the interval to the top.
Many marginal fields in this basin have become uneconomical because of the high cost and complexity of sand control methodology. Therefore, reducing costs and time becomes vital to help ensure economic viability, as well as achieving significant operational efficiencies. Additionally, reducing near-wellbore (NWB) mechanical skin and ensuring good productivity from the reservoir are among the major solutions when implementing an MSSE completion. The methodology adopted significantly helped reduce expenditures by standardizing completion design, simplifying the core complexity, and enhancing overall reliability and operational efficiency. The optimized engineering workflow was fit for purpose, rather than the conventional “cookie-cutter” method to address sanding propensity in this field.
This paper discusses the cutting-edge MSSE completion systems that focused on downhole completion and modifications for pumping operations. Additionally, the paper reviews challenges addressed during this campaign, workflow adapted, detailed strategy success factors, and positive results obtained during evaluation. This has helped reduce potential risks and improve reliability and performance, which can act as best practices and can be applied within similar fields.