Pressure and rate analysis in unconventional reservoirs
File(s)
Author(s)
Marsden, Joseph
Type
Thesis
Abstract
The aim of this work is to develop a realistic conceptual shale gas reservoir model that explains the observed behaviour of Haynesville wells and can predict their future behaviour.
A model developed by Kostyleva (2019) consists of a two zone repetitive element for each set of wellbore perforations. A fractured zone is in contact with the wellbore and surrounded by a matrix zone representing the rock unaffected by fracturing. The two zones have different initial permeabilities. The matrix permeability decreases as soon as its pore pressure begins to fall. The decline in fractured zone permeability starts below a threshold pressure. Later, a pseudo-skin factor is introduced and increases with time. The validation of Kostyleva’s (2019) model is continued by accurately simulating the dynamic pressure behaviour of 8 Haynesville Shale wells from the period 2014 – 2016.
Two components of Kostyleva’s (2019) model seem unrealistic. Any pressure drop in a region intended to represent the network of fractures around a wellbore should cause an immediate fall in its permeability. Field observations do not support the existence of an actual skin factor. Therefore, the present study proposes a new Multiple Fracture Zone (MFZ) model. Each perforation set is surrounded by several zones. Each zone represents a volume of shale containing both matrix and fractures and has a different permeability-pressure relationship. Fractures in zones nearer the wellbore contain more proppant and are less compressible. Any pressure drop decreases permeability and no pseudo-skin factor needs to be introduced.
The MFZ model has been validated by accurately simulating the dynamic pressure behaviour of 8 Haynesville Shale wells from the period 2014 – 2018.
A model developed by Kostyleva (2019) consists of a two zone repetitive element for each set of wellbore perforations. A fractured zone is in contact with the wellbore and surrounded by a matrix zone representing the rock unaffected by fracturing. The two zones have different initial permeabilities. The matrix permeability decreases as soon as its pore pressure begins to fall. The decline in fractured zone permeability starts below a threshold pressure. Later, a pseudo-skin factor is introduced and increases with time. The validation of Kostyleva’s (2019) model is continued by accurately simulating the dynamic pressure behaviour of 8 Haynesville Shale wells from the period 2014 – 2016.
Two components of Kostyleva’s (2019) model seem unrealistic. Any pressure drop in a region intended to represent the network of fractures around a wellbore should cause an immediate fall in its permeability. Field observations do not support the existence of an actual skin factor. Therefore, the present study proposes a new Multiple Fracture Zone (MFZ) model. Each perforation set is surrounded by several zones. Each zone represents a volume of shale containing both matrix and fractures and has a different permeability-pressure relationship. Fractures in zones nearer the wellbore contain more proppant and are less compressible. Any pressure drop decreases permeability and no pseudo-skin factor needs to be introduced.
The MFZ model has been validated by accurately simulating the dynamic pressure behaviour of 8 Haynesville Shale wells from the period 2014 – 2018.
Version
Open Access
Date Issued
2021-07
Date Awarded
2023-11
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Gringarten, Alain
Blunt, Martin
Publisher Department
Earth Science & Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Master of Philosophy (MPhil)