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Design of Acid Re-Stimulation Treatments Using Transient Pressure Analysis

IP.com Disclosure Number: IPCOM000246440D
Publication Date: 2016-Jun-06
Document File: 6 page(s) / 251K

Publishing Venue

The IP.com Prior Art Database

Abstract

The current work describes a workflow for the application of pre-treatment transient pressure analysis to identify near wellbore damage during acid re-stimulation treatments. The primary purpose of the workflow is to identify presence of adjacent pre-existing wormholes and residual damage in a partially stimulated layer for optimal design of the re-stimulation acidizing treatment.

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      Design of Acid Re-Stimulation Treatments Using Transient Pressure AnalysisAbstract

The current work describes a workflow for the application of pre-treatment transient pressure analysis to identify near wellbore damage during acid re-stimulation treatments. The primary purpose of the workflow is to identify presence of adjacent pre-existing wormholes and residual damage in a partially stimulated layer for optimal design of the re-stimulation acidizing treatment.

Background

For a damaged formation a damage skin is determined. For the design of the acid stimulation treatment of the formation the skin information is used to quantify the damage zone (damage permeability and depth) near the wellbore. However, in case of a partially stimulated zone two regions may exist near the wellbore which have permeability different than the native permeability of the reservoir - a high permeability region, which can be a wormhole formed due to previous stimulation treatment and a damaged region, which could be the residual damage which could not be removed from previous stimulation treatments. Identification of these regions is essential to accurately design the re-stimulation of the zone. A single damage skin for partially stimulated zones may be incorrectly interpreted and lead to sub-optimal design of the re-stimulation treatment. For example, a negative skin may be interpreted as an absence of damage or even a thief zone. This may not be true as damage may still be present in a layer with a negative damage skin for carbonate formations. Similarly, for a layer with positive skin pre-existing wormholes may be ignored while it is possible that wormholes are present in a layer with a positive damage skin. Acid spending in pre-existing wormholes is different from acid spending in matrix flow. Further, the fluids which have shear dependent rheology will behave differently in the wormhole compared to the matrix. Hence, for an effective re-stimulation acidizing treatment design (fluid selection and placement) identification of pre-existing wormholes and residual damage in the partially stimulated layers is essential.

Previous Work

Olarewaju (1990) has discussed about the use of transient pressure data for determining the extent and depth of permeability alteration around the wellbore. However, in the work only a single zone of altered permeability around the wellbore was considered which cannot be used to represent the simultaneous presence of a wormhole and damaged zone. Similarly, El-Khatib (2009) & El-Khatib (2011) discussed about the use of transient pressure data for determining the extent and depth of permeability alteration in a single zone around the wellbore with permeability varying from wellbore radius to the depth of permeability alteration. Zhang and XuanLi (2011) have discussed the application of transient pressure for determining the permeability of 2 adjacent layers. Similarly, Kucuk and Luis (1989) have described a method to determi...