Rate-Transient Analysis of Tight Oil and Gas Reservoirs
Abstract
Horizontal wells completed in multiple hydraulic fracturing stages (multi-fractured horizontal wells or MFHWs) have been critical technologies applied to low-permeability (tight) oil and gas reservoirs in recent decades, resulting in commercial production. For each stage in a MFHW, the formation is fractured by injecting water and sand at high pressure. The resulting hydraulic fracture system enhances production from tight reservoirs by increasing the effective area for flow of the reservoir fluids. Therefore, fracture conductivity and total fracture area are key parameters affecting MFHW performance. A powerful tool for characterization of MFHWs is rate transient analysis (RTA); RTA models are commonly based on analytical solutions to fluid flow equations describing flow through the rock matrix and hydraulically-induced fractures to MFHWs. In addition to MFHW characterization, RTA is used for short- and long-term production forecasting (or estimation of ultimate recovery) and estimation of fluid-in-place.
In order to obtain analytical solutions to the flow equations (for RTA purposes), simplifying assumptions have been made by practitioners such as constant formation permeability, constant properties of oil, constant hydraulic diffusivity of gas, and single-phase flow of the primary hydrocarbon phase. In this thesis, each of these assumptions are relaxed and corresponding analytical/semi-analytical solutions are developed for tight oil and gas reservoirs. Three methods are proposed for incorporation of the aforementioned nonlinearities into RTA. The methods utilize 1) the transformation of nonlinearity approach, 2) the iterative integral approach, and 3) the dynamic drainage area concept. The results of the proposed methods are compared against numerical simulation for validation, and are applied to field cases to demonstrate practical utility. Importantly, it is demonstrated that failure to incorporate corrections for the aforementioned nonlinearities into RTA can lead to significant errors in derived parameters, such as the linear flow parameter derived from transient linear flow analysis.
The RTA methods developed in this thesis are intended to provide practitioners with more robust tools for analysis of tight oil and gas reservoirs.
Description
Keywords
Engineering--Petroleum
Citation
Qanbari, F. (2017). Rate-Transient Analysis of Tight Oil and Gas Reservoirs (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/27535