The Production of Chemical Reaction-Induced High-Pressure Gas Pulses for Rock Fracturing

Abstract

Past research has shown that gas generating reactions that produce high borehole pressures by ramping up to the pressures slowly can be useful in producing fracturing around a borehole without damaging it. Most chemical reactions used for high-pressure gas fracturing have produced the gas by using a single component reaction, such as the ignition of nitrocellulose. Two-component solid-liquid and liquid-liquid reactions are examined in this report to determine if a gas-producing reaction suitable for use in borehole fracturing can be developed. Surface passivation effects make it difficult to produce useful solid-liquid reactions. Laboratory and field tests using a liquid-liquid system (triethylaluminum and water) demonstrated that liquid phase reactions will proceed with the speed and peak pressure needed to produce useful fracturing. The field testing also showed that with suitable precautions triethylaluminum could be safely handled in a borehole. Liquid-liquid chemical reaction systems (such as triethylaluminum and water) offer advantages, in that the pressure pulse can be regulated by modifying the reactants or designing the downhole container to control the mixing of the reactants. In the case of triethylaluminum, there are additional advantages, in that the reactive compound is pyrophorlc, not explosive, and the products from the water-triethylaluminum reaction (ethane and aluminum oxide) are not toxic.