A novel radial jet drilling stimulation technique for enhancing heat recovery from fractured geothermal reservoirs

S Salimzadeh,M Grandahl,M Medetbekova,H.M Nick

doi:10.1016/j.renene.2019.02.073

Abstract

In this study, the application of the Radial Jet Drilling (RJD), a novel stimulating technique for enhancing productivity in the existing wells in deformable naturally fractured reservoirs was investigated using a robust three-dimensional finite element DFM (discrete fracture-matrix) model. Results showed that the RJD laterals were more effective in enhancing injectivity/productivity in cases with lower fracture density, i.e. lower equivalent permeability, while they had no significant effect on the heat production in these cases. In higher fracture density cases, the RJD laterals improved the heat production while had no significant effect on the injectivity/productivity. Results also showed that in reservoirs with very low permeability matrix, the RJD laterals can be used to connect the wells to the fracture network and hence enhance the well performance. The sensitivity analysis on the average net energy production rate with respect to the length of the RJD laterals showed that in the situations where the wells were not connected directly to the fractures, the length of RJD laterals played a crucial role in enhancing the average net energy rate. However, the 100 m laterals almost removed the dependency of the average net energy production rate on the well placement for low, medium and high fracture density cases.

Highlights

Fossil fuels are still the main contributor in energy market around the world, concerns regarding the security of energy, climate change and carbon emissions have encouraged developing strategic plans towards low carbon future by relying on renewable energy resources (Bruckner et al [52])
Geothermal energy has the potential to integrate with other sources of energy to improve the overall energy production and make the heat production economically attractive
Several recent studies have investigated the utility of Radial Jet Drilling (RJD) laterals for well stimulation and well flow enhancement (e.g. [30]), to the best knowledge of authors, a comprehensive study of the application of RJD technique in fractured geothermal reservoirs is missing and the present study aims to fill the gap

Summary

Introduction

Fossil fuels are still the main contributor in energy market around the world, concerns regarding the security of energy, climate change and carbon emissions have encouraged developing strategic plans towards low carbon future by relying on renewable energy resources (Bruckner et al [52]). Geothermal energy stored in the Earth's crust is one of the promising and clean renewable energy resources in the world [1,2]. Geothermal energy is extracted from the earth's crust by drilling injection and production wells, and the so-called doublet system in which cold fluid (i.e. water) is injected at the injection well and the hot water or steam is produced from the production well, is very popular in geothermal sites around the world [4]. The geothermal systems rely on the injected fluid being able to flow from the injection well to the production well through the reservoir, either using the natural permeability of the formation [5,6] or fractures in the formation as flow paths [7]. The formations are typically of very low permeability, and fractures, natural or man-made, are needed to enhance the fluid flow within these reservoirs

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Results

Conclusion