The effect of natural fracture characteristics on current analytical models for hydraulically fractured unconventional shale reservoirs.

摘要

In recent years, the oil and gas industry has shifted its focus more towards unconventional shale reservoirs. It has become apparent that these reservoirs require a significant amount of fracturing in order to be productive. This being the case, many analytical models have been developed over the years to predict the performance of these extensively naturally and hydraulically fractured reservoirs.;This thesis presents an investigation of two analytical reservoir models for hydraulically fractured unconventional shale wells. The main focus of this research is to investigate the effect of the natural fracture network characteristics on the response from the two models. In addition, the sensitivity of each model to other input parameters was explored. Furthermore, this thesis also presents an attempt to match the responses generated by these two models. The two models are Al-Ahmadi's triple porosity, dual fracture model that assumes slab matrix geometry and Apaydin's dual porosity trilinear-flow model. The assumptions and geometric layouts of these models are described, and the pertinent equations behind these two models are provided with a calculation procedure outlined.;Once the sensitivity runs were completed, it was found that both of the models were the most sensitive to the permeability and porosity of the matrix as well as the thickness of the formation. This makes sense because these parameters ultimately dictate the amount of oil/gas that exists as well as how easily it is able to flow through the system. Additionally, the natural fracture spacing/number of natural fractures in the model was the next most important variable in all cases. The natural/hydraulic fracture characteristics, as well as all of the other parameters that were tested, acted to change the time it took for each of the models to reach its absolute production limit.;It was found, however, that any match between them would be entirely subjective. This is true despite the many modifications made to both of the models to make them as similar as possible. It was concluded that the two models are fundamentally different in how they represent the flow of hydrocarbons through fracture networks in hydraulically fractured unconventional shale wells. Overall, this research shows that different representations of the natural fracture network can significantly affect the production response.