Effective Approach to Wellbore Clean Out Operation: A Case Study from Zawtika Phase 1B

Abstract

Free sand movement and fines mobilization during production in Zawtika field is one of the main challenges and can result in failures of production systems leading to SSHE exposure, loss of production or even well suspended. The optimum completion design Cased Hole Gravel Pack (CHGP) allows the well to maintain solid-free gas production with (limiting skin) selectivity, longevity and integrity throughout the life cycle. The Sand Control completion deployment, effectiveness and well productivity is directly related to the cleanliness of cased well bore and completion brine. The Total Solid Suspension (TSS) and Nephelometric Turbidity Units (NTU) or clarity of the fluid is the key indicator of well cleanliness. Zawtika Phase 1A post job review highlighted that Wellbore Cleanout (WBCO) is one of the most time consuming operation. To overcome this challenge and create areas of opportunities for improvement based on efficiencies, several possible solutions identified below. Excessive pipe dope, metal debris and rust from casing can collect within the well bore, bridge in perforation tunnels and ultimately damage reservoir or seriously hinder running completion components. The correct combination of Pipe Dope applying procedure, Chemical Displacement, Mechanical Movement and Hydraulic Displacement are the main key contributing factors to improved operation safety, deployment operational efficiency. Lab scale test conducted to simulate test for pipe dope removal chemical, Mechanical Casing Scraper and casing brush simulate testing in order to remove casing vanishing coating, also applying wellbore cleaning concept from drilling - rotational, pump rate and trip speed Recovery of metal or other debris in a limited number of runs gives several advantages: - Minimize reservoir damage - Reduces risks of screen plugging - Saves rig time. This paper will describe planning process, pipe dope procedure, wellbore clean out chemical / mechanical tool selection based on laboratory testing, displacement techniques, and operation summary. The potential cost saving to project can be more than 5 Million USD. The combination of this improvement in WBCO operation is able to reduce the operation time and cost in Phase 1B more than 71% comparing to Phase 1A performances in 2014-2015