Understanding the performance of hydraulically fractured wells in the laumontite-rich tight glutenite formation

Abstract

Massive hydraulic fracturing treatments have been used to produce hydrocarbons from tight glutenite oil reservoirs through both vertical and horizontal wells. Some tight glutenite reservoirs are rich in laumontite. Field experiences indicate that the performance of hydraulically fractured wells on this type of laumontite-rich tight glutenite reservoir typically resulted in low oil productivity and quickly declining oil rates. To understand the poor well performance of these laumontite-rich tight oil wells, extensive laboratory and numerical simulation studies have been conducted to explore the major controlling factors. Laboratory results indicate that the laumontite-rich glutenite reservoir rock has the following characteristics: 1) reservoir permeability is sensitive to stress conditions; 2) reservoir rock has low mechanical strength; and 3) reservoir rock has a low elastic modulus. These geomechanical deformation characteristics strongly affect the well productivity on the laumontite-rich formations. During the hydraulic fracturing and well production phases, the reservoir rock near the main hydraulic fracture can be compacted significantly to reduce rock porosity and permeability. As a result, the fluid flow capacity from the reservoir rock into the hydraulic fracture is reduced. By using laboratory testing data, fully coupled flow-deformation finite element simulations were conducted to study the impact of rock compaction/dilation on well productivity. Based on the numerical simulations, a new hydraulic fracturing scheme was proposed, and a field pilot test was conducted on one vertical well in the study area. Promising field oil production rates were achieved. This paper presents our understanding of the laboratory data, numerical simulation, and field pilot tests results. The new hydraulic fracturing scheme was based on the rock dilation near the main hydraulic fracture. The result indicates that rock dilation, if proactively utilized, can enhance the fluid deliverability from the reservoir into the main hydraulic fracture and boost well productivity.