Successful Implementation of Through Tubing Technology(Sand Control and Gas Lift)in Challenging Offshore Environment as an Integrated Development Strategy for Sustainable Development of Marginal Fields:A Case Study

摘要

Well AB-5 was drilled&completed in a marginal field in offshore West coast of India.Initially well produced only gas,till the oil bearing sands were perforated&it was being put on commingled oil&gas production.Through tubing sand control was installed in the well in view of continuous sand fill observed post perforation due to unconsolidated sand formation.Over the period of time,formation pressure depleted and the well eventually load up&died in absence of any mode of artificial lift on the unmanned platform.The Challenge was to unload&activate the well using gas lift in a commercially viable manner,avoiding expensive Barge based operation without having the said facility&provisions available. Since no Gas Lift Mandrel was present in the upper completion,a Thru-tubing Gas lift technique using retrievable straddle packers with GLV in between&conveyed on slick line was being adopted.A temporary arrangement of nitrogen tanks, pumps&surface set up for subsequent well unloading was organized.Further,a 20 T modular crane was installed on the platform after a detailed platform structural load analysis for spotting the surface equipment.Detailed NODAL analysis was being carried out for modeling the required nitrogen rates and the well performance at different gas lift parameters.Post GLV installation,nitrogen was pumped thru the annulus via the GLV,installed against circulating SSD,into the tubing. This Paper not only describes the Job design,technique implemented&challenges overcome during successfully activating a theoretically dead well to approx.1000 BOPD production,thus establishing the viability of Through Tubing Sand Control (TTSC)&Thru-Tubing Gas Lift(TTGL)technologies but also delivers an integrated development strategy for sustainable development of marginal fields. The same technology is now being implemented in other water loaded wells of the field having similar technical and logistical constraints.