Study on Wormhole Coverage, Foamy Oil Phenomenon, and Well Interference of Cold Heavy Oil Production with Sand Wells

Date
2012-12
Authors
Xiao, Lei
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Publisher
Faculty of Graduate Studies and Research, University of Regina
Abstract

In Cold Heavy Oil Production with Sand (CHOPS) wells, the presence of wormholes is considered to be one of the most important factors that contribute to enhanced production rate. Quantitative detection of wormholes can offer important parameters in further optimization of post-CHOPS processes such as post-CHOPS EOR planning and infill well drilling. Moreover, foamy oil is one of the most complex phenomena in CHOPS wells because gas starts mixing with oil and forming relatively continuous foam with high compressibility once the pressure drops to a certain point during depletion. A CHOPS reservoir with two zones including a foamy oil zone and an original heavy oil bank might be possible, and it is of great importance to model such reservoirs by considering distinct foamy oil properties in comparison with original heavy oil. Finally, interference among multiple CHOPS wells with wormholes is still unknown. Before any post-CHOPS EOR plan, it is worth knowing how different CHOPS wells affect each other with the possible existence and connection of wormholes. In this thesis, a concept of effective wormhole coverage is proposed to detect wormhole coverage quantitatively in a practical engineering manner. A corresponding new CHOPS well model has been developed and solved using semi-analytical approaches based on source and sink function methods. Transient pressure and production analysis technology has provided powerful tools to determine effective wormhole coverage quantitatively with high accuracy. Secondly, a composite model with PVT properties discontinuity between foamy oil and original heavy oil zones was used to investigate composite behaviours of CHOPS reservoirs with both foamy oil zones and original heavy oil banks. Pseudo variables of pressure and time have been used to linearize partial differential equations (PDE) with non-linearity caused by high compressibility and pressure-dependent properties. Finally, a multiple CHOPS wells model, which describes several CHOPS wells with various wormhole configurations existing in the same reservoir, has been developed to study interference among multiple CHOPS wells. All models have been validated with either analytical or numerical solutions and can be used to analyze pressure and production data of CHOPS wells from most Canadian cold heavy oil production fields.

Description
A Thesis Submitted to the Faculty of Graduate Studies and Research In Partial Fulfillment of the Requirements for the Degree of Masters of Applied Science in Petroleum Systems Engineering, University of Regina. xvi, 132 l.
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