Investigating the efficacy of proppant in maintaining open cracks following hydraulic fracturing

Abstract

Hydraulic fracturing is used as one of the most effective well stimulation methods, with long-lasting effect, in order to enhance the effective permeability of the low permeability reservoir rocks, and to increase the production rate. In this thesis, the key aspects of the hydraulic fracturing, such as their mechanics, geometry and design are reviewed. Predominantly, the key challenges and motivation behind the process are mentioned, and the principal objectives of the following experiments have been identified. The theoretical background on the hydraulic fracturing, proppant, it’s influence on maintaining of hydraulic fractures, the mechanics of hydraulic fracturing, related industry challenges, several types of stimulations and innovations are talked over in one of the chapters. Experimental work, which illustrates the behavior of the shale formations during the proppant placement is performed in laboratory. Two experiments are carried out: with cube-shaped sample and two cylindrical stack-on samples. The experiment consists of testing the propping agent under the load in uniaxial test machine in different conditions: filling the V-shaped crack of the cube in the cube experiment and testing a thin layer of proppant between two concrete cylindrical samples. The samples for these experiments are previously cast in the cement lab. Test results are obtained and converted into the spreadsheet form at the end of the experiments, and then presented in the graph form afterwards. Typical stress/strain plot can be observed on following graphs, and for specific types of proppant, some trend can be distinguished. Later the difference between the various types of propping agents are given as well. After the samples collapsed, the grains are thoroughly inspected under the microscope. The possible sources of errors are further listed, main problems associated with the experimentation are scrupulously discussed and additional recommendations for future work are provided. The foremost outcome can be acknowledged, as with the increase of density of the propping agent, the strength of the rock can be upgraded, and hydraulic fracturing done with the higher density proppant can better withstand the overburden confining pressure