Rate-Transient Analysis of Tight Gas Condensate and Black Oil Wells Exhibiting Two-phase Flow

Date
2016-01-27
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Abstract
Quantitative Production Data Analysis (PDA) is a popular petroleum reservoir engineering technique that is employed to derive information about reservoir properties and well stimulation (hydraulic fractures). Rate-Transient Analysis (RTA), which is an advanced form of PDA, uses well flowing well pressures along with production rates to extract this information. Although mathematical models used for RTA are reasonably mature for conventional reservoirs, there are complexities associated with reservoir fluid storage and flow behavior that impede direct adaptation of these methods for low-permeability (tight), unconventional reservoirs. For example, wells producing from tight unconventional reservoirs may exhibit lengthy periods of transient flow, during which time multi-phase flow could occur. The primary objective of this thesis is to demonstrate that analytical RTA techniques may be adapted to quantitatively analyze and forecast wells producing from tight unconventional reservoirs exhibiting single− and multi-phase flow during the transient linear and boundary-dominated flow periods. In particular, multi-fractured horizontal wells (MFHWs) producing from tight gas condensate and oil reservoirs and exhibiting long-term transient linear flow are studied. Several commonly observed behaviors associated with MFHWs producing from tight reservoirs, such as constant gas-oil-ratios (GORs) during the transient linear flow, are explained analytically. Modified pseudovariables, critical for linearizing the diffusivity equation for describing multi-phase flow, are developed that allow the liquid-solution analogy to be applied to the transient linear and boundary-dominated flow versions of the diffusivity equation. Novel techniques for calculation of saturation pressure relationships, required for pseudovariable evaluation, are developed. Solutions that utilize modified pseudovariables are applied to both inverse and forward modeling of wells producing from these reservoir types. The accuracy of the new analytical approaches is demonstrated through comparison to numerical simulation, and practical utility through analysis of field cases. A secondary objective is to demonstrate the use of black oil simulation and surface fluid rate recombination techniques, combined with assisted history-matching techniques, to extract reservoir, hydraulic fracture and in-situ fluid compositions from MFHWs completed in tight gas condensate reservoirs. The analytical techniques developed in this thesis will be useful for petroleum engineers who employ analytical techniques in tight unconventional reservoir and hydraulic-fracture characterization.
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Keywords
Engineering, Engineering--Petroleum
Citation
Behmanesh, H. (2016). Rate-Transient Analysis of Tight Gas Condensate and Black Oil Wells Exhibiting Two-phase Flow (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/27534