Legal Issues in Hydraulic Fracturing



Legal Issues in Hydraulic Fracturing

Introduction

Hydraulic fracturing consists of injecting a high pressure fluid in a wellbore to a predetermined depth. When the pressure applied by the fluid compensates lithostatic load (the weight of the rock above the place where the pressure is applied), and increases local resistance of the rock, a crack is initiated and then can be spread over several hundred meters, provided that the fluid is injected sufficient for maintaining a pressure sufficient to maintain the load. During the process, a propant (usually sand or ceramic balls) is injected in order to prevent closure of the fissure. The drilling water contains additives suitable for the type of bedrock, to facilitate the fracturing operation and support of the cracks. Cracks resulting behave as drains, thereby making available for the production of gas volume of rock, removed from the wellbore, but close to the drain created.

Discussion

Background

Hydraulic fracturing was first applied to classical geological reservoirs. Its use in the case of low permeability fields Tight Gas Reservoirs called TGR (thousand times less permeable than conventional reservoirs), and has faced real difficulties. The TGR which contains gas recovery rates, when using conventional methods, remains modest with 3-10% of the hydrocarbons in place. Hydraulic fracturing can increase returns (Ragsdale, 1992). The gas collected from a volume of rock located near the surface of the crack will migrate due to the pressure difference. Gas production is to drain the area whose permeability is low.

This technique has its limitations: the efficiency is increased, but once the drainage is performed, production undergoes a very rapid decrease. The gas drained areas remain inaccessible. Shale combine this difficulty, due to the low permeability of the rock (that is to say its low ability to pass through it fluid) with a natural heterogeneity of the environment. Whether conventional or unconventional gas is mainly composed of methane and has identical chemical properties as a result of the maturation of the bedrock (Rahm, 2011). However, the difference between the gas and unconventional gas is that the latter is traditionally operated by vertical wells due to the nature of the geological formations in which they are trapped. Because of this feature, the non-conventional gas is thus by definition associated with the so-called unconventional way to exploit them.

Thus, depending on the physical characteristics of the rocks that trap, three types of unconventional gas are now produced around the world: coal gas, the Tight Gas and Shale Gas or shale gas. The first type of gas is largely adsorbed on the surface of the coal and its extraction requires generally simple pumping interstitial water contained in the coal. In the case of Tight Gas and Shale Gas, hydrocarbons are contained in a diffuse manner at very low permeability formations. Therefore, the techniques used for their extraction are highly complex and are to stimulate the rock containing the gas to give permeability that does not naturally possess. The process used to recover these gases based on two technologies: horizontal drilling and ...