Analyzing Limited Steam Chest Collapse in Thermal Oil Recovery: Insights from Field Data

Abstract Steam injection has played a pivotal role in the evolution of Enhanced Oil Recovery (EOR) techniques, significantly enhancing hydrocarbon extraction from reservoirs. Applied mainly in heavy oil reservoirs where other forms of EOR are less effective, steam injection has proven to be a mainstay EOR method since the 1960s. However, developments are still being taken to understand the intricacies of the steam injection process in the field. The findings presented are derived from extensive field data analysis on a steam injection field in Oman with more than 40 years of history, where steam is continuously injected in an inverted nine spot pattern steam drive project. The analytical evaluation of producers-injector communication reveals novel insights into the performance, efficiency, and optimization of steam injection for optimal extraction of hydrocarbons. It was found that the behavior of water cut in producers can be adversely affected by shutting in nearby communicating injectors, especially, when an injector is shut in for a short duration and then started again. This does not allow enough time for the condensed water in the channels between the injector and producer to be withdrawn. This results in a waterfront development from this unflushed water which gets pushed from the injector to the producer, significantly increasing the water cut. Field behavior has shown, the stopping of a steam injector can, in some cases, increase the water cut of nearby communicating producers. Steam injectors form pathways to producers, these pathways get heated and retain that heat as long as steam is injected. Both steam and oil flow in these channels. Intermittent shut ins of steam injectors interrupt the steam propagation within these pathways and introduces an imbalance in the system. Cooling the fluids in the reservoir will condense the steam and without the pressure drive from the injector, the water remains in the reservoir until the injection starts again. Once injection is started again, the pressure drive pushes the condensed water into the producer. The unfavorable mobility ratio of oil resulting from reservoir cooling, yield more water production compared to when the injector was running continuously. The study investigates the physics behind the intermitting steam interruption and its implications on well and reservoir management, especially, steam injection strategy and how to minimize oil loss from intermittent steam injector shut in.