Initiation of Stimulation Treatments Depends on Wellbore Mechanical Responses During Drilling

Research output: Contribution to conferencePaper

Abstract

A stimulation treatment follows from, and is affected by, the set of processes that occur during well construction. The creation of the opening causes a major change in stress state, and may involve permanent rock deformations affecting the wall of the wellbore. Drilling practices seek to avoid such failures because of the immediate consequences associated with rock debris loading the well, but also because deformations provide pathways for fluids to invade the rocks where they may lead to further de-stabilisation via chemical interactions. A hydraulic stimulation treatment uses the pressures of injected fluids to cause rock breakage over a short period of time, creating new flow pathways. The mechanics of the stimulation process, at the moment of its initiation, is very like the condition of mud overbalance while drilling, where the wellbore is inflated to a larger-diameter condition. In stimulation treatments, this wellbore inflation and the resulting rock deformation responses, occur in a situation that already has been modified by the drilling actions.
We describe numerical simulations of these near-well geomechanical processes, relating both to drilling and to stimulation activities, using a method that is based on a combined finite-discrete element formulation. The 2D numerical method treats the model domain initially as a continuum, but allows fractures to develop along any of the faces of the finite elements, with composite fractures able to grow into large and complex configurations. We show that an important factor is the removal of the rock mass from the drilled hole, which leads to a very different stress state around the opening compared to mathematical models that have a pre-existing hole in them. Depending on the far-field stress state and the material properties, the simulations of drilling often develop fracture arrays that are associated with borehole elongation in the far-field minimum stress direction (which is compatible with standard knowledge). Those arrays alter the near-well stress state in major ways. The numerical simulations also reveal the characteristics of deformation processes, involving fracturing and consequent strain changes, and thus their stress changes, which affect the part of the wellbore wall that is broadly aligned with the maximum far field stress. Except with the strongest and stiffest rocks, the fractures in this region initiate and develop mainly as shears, which contrasts sharply with the received wisdom for what is expected. This response also applies when we impose a stimulation loading inside the wellbore (fluid injection).
Original languageEnglish
Number of pages13
StatePublished - Jun 2017
EventSPE EUROPEC 2017 at the 79th EAGE Conference and Exhibition - Paris, France

Conference

ConferenceSPE EUROPEC 2017 at the 79th EAGE Conference and Exhibition
CountryFrance
CityParis
Period12/06/1715/06/17

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stimulation
rocks
rock
Rocks
drilling
Drilling
far fields
simulation
well
Fluids
Economic Inflation
causes
fluids
stress field
fluid
Computer simulation
fluid injection
mud
fracturing
destabilization

Cite this

Alruwaili, K., Couples, G. D., & Ma, J. (2017). Initiation of Stimulation Treatments Depends on Wellbore Mechanical Responses During Drilling. Paper presented at SPE EUROPEC 2017 at the 79th EAGE Conference and Exhibition, Paris, France.

Alruwaili, Khalid; Couples, Gary Douglas; Ma, Jingsheng / Initiation of Stimulation Treatments Depends on Wellbore Mechanical Responses During Drilling.

2017. Paper presented at SPE EUROPEC 2017 at the 79th EAGE Conference and Exhibition, Paris, France.

Research output: Contribution to conferencePaper

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abstract = "A stimulation treatment follows from, and is affected by, the set of processes that occur during well construction. The creation of the opening causes a major change in stress state, and may involve permanent rock deformations affecting the wall of the wellbore. Drilling practices seek to avoid such failures because of the immediate consequences associated with rock debris loading the well, but also because deformations provide pathways for fluids to invade the rocks where they may lead to further de-stabilisation via chemical interactions. A hydraulic stimulation treatment uses the pressures of injected fluids to cause rock breakage over a short period of time, creating new flow pathways. The mechanics of the stimulation process, at the moment of its initiation, is very like the condition of mud overbalance while drilling, where the wellbore is inflated to a larger-diameter condition. In stimulation treatments, this wellbore inflation and the resulting rock deformation responses, occur in a situation that already has been modified by the drilling actions.We describe numerical simulations of these near-well geomechanical processes, relating both to drilling and to stimulation activities, using a method that is based on a combined finite-discrete element formulation. The 2D numerical method treats the model domain initially as a continuum, but allows fractures to develop along any of the faces of the finite elements, with composite fractures able to grow into large and complex configurations. We show that an important factor is the removal of the rock mass from the drilled hole, which leads to a very different stress state around the opening compared to mathematical models that have a pre-existing hole in them. Depending on the far-field stress state and the material properties, the simulations of drilling often develop fracture arrays that are associated with borehole elongation in the far-field minimum stress direction (which is compatible with standard knowledge). Those arrays alter the near-well stress state in major ways. The numerical simulations also reveal the characteristics of deformation processes, involving fracturing and consequent strain changes, and thus their stress changes, which affect the part of the wellbore wall that is broadly aligned with the maximum far field stress. Except with the strongest and stiffest rocks, the fractures in this region initiate and develop mainly as shears, which contrasts sharply with the received wisdom for what is expected. This response also applies when we impose a stimulation loading inside the wellbore (fluid injection).",
author = "Khalid Alruwaili and Couples, {Gary Douglas} and Jingsheng Ma",
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Alruwaili, K, Couples, GD & Ma, J 2017, 'Initiation of Stimulation Treatments Depends on Wellbore Mechanical Responses During Drilling' Paper presented at SPE EUROPEC 2017 at the 79th EAGE Conference and Exhibition, Paris, France, 12/06/17 - 15/06/17, .

Initiation of Stimulation Treatments Depends on Wellbore Mechanical Responses During Drilling. / Alruwaili, Khalid; Couples, Gary Douglas; Ma, Jingsheng.

2017. Paper presented at SPE EUROPEC 2017 at the 79th EAGE Conference and Exhibition, Paris, France.

Research output: Contribution to conferencePaper

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T1 - Initiation of Stimulation Treatments Depends on Wellbore Mechanical Responses During Drilling

AU - Alruwaili,Khalid

AU - Couples,Gary Douglas

AU - Ma,Jingsheng

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N2 - A stimulation treatment follows from, and is affected by, the set of processes that occur during well construction. The creation of the opening causes a major change in stress state, and may involve permanent rock deformations affecting the wall of the wellbore. Drilling practices seek to avoid such failures because of the immediate consequences associated with rock debris loading the well, but also because deformations provide pathways for fluids to invade the rocks where they may lead to further de-stabilisation via chemical interactions. A hydraulic stimulation treatment uses the pressures of injected fluids to cause rock breakage over a short period of time, creating new flow pathways. The mechanics of the stimulation process, at the moment of its initiation, is very like the condition of mud overbalance while drilling, where the wellbore is inflated to a larger-diameter condition. In stimulation treatments, this wellbore inflation and the resulting rock deformation responses, occur in a situation that already has been modified by the drilling actions.We describe numerical simulations of these near-well geomechanical processes, relating both to drilling and to stimulation activities, using a method that is based on a combined finite-discrete element formulation. The 2D numerical method treats the model domain initially as a continuum, but allows fractures to develop along any of the faces of the finite elements, with composite fractures able to grow into large and complex configurations. We show that an important factor is the removal of the rock mass from the drilled hole, which leads to a very different stress state around the opening compared to mathematical models that have a pre-existing hole in them. Depending on the far-field stress state and the material properties, the simulations of drilling often develop fracture arrays that are associated with borehole elongation in the far-field minimum stress direction (which is compatible with standard knowledge). Those arrays alter the near-well stress state in major ways. The numerical simulations also reveal the characteristics of deformation processes, involving fracturing and consequent strain changes, and thus their stress changes, which affect the part of the wellbore wall that is broadly aligned with the maximum far field stress. Except with the strongest and stiffest rocks, the fractures in this region initiate and develop mainly as shears, which contrasts sharply with the received wisdom for what is expected. This response also applies when we impose a stimulation loading inside the wellbore (fluid injection).

AB - A stimulation treatment follows from, and is affected by, the set of processes that occur during well construction. The creation of the opening causes a major change in stress state, and may involve permanent rock deformations affecting the wall of the wellbore. Drilling practices seek to avoid such failures because of the immediate consequences associated with rock debris loading the well, but also because deformations provide pathways for fluids to invade the rocks where they may lead to further de-stabilisation via chemical interactions. A hydraulic stimulation treatment uses the pressures of injected fluids to cause rock breakage over a short period of time, creating new flow pathways. The mechanics of the stimulation process, at the moment of its initiation, is very like the condition of mud overbalance while drilling, where the wellbore is inflated to a larger-diameter condition. In stimulation treatments, this wellbore inflation and the resulting rock deformation responses, occur in a situation that already has been modified by the drilling actions.We describe numerical simulations of these near-well geomechanical processes, relating both to drilling and to stimulation activities, using a method that is based on a combined finite-discrete element formulation. The 2D numerical method treats the model domain initially as a continuum, but allows fractures to develop along any of the faces of the finite elements, with composite fractures able to grow into large and complex configurations. We show that an important factor is the removal of the rock mass from the drilled hole, which leads to a very different stress state around the opening compared to mathematical models that have a pre-existing hole in them. Depending on the far-field stress state and the material properties, the simulations of drilling often develop fracture arrays that are associated with borehole elongation in the far-field minimum stress direction (which is compatible with standard knowledge). Those arrays alter the near-well stress state in major ways. The numerical simulations also reveal the characteristics of deformation processes, involving fracturing and consequent strain changes, and thus their stress changes, which affect the part of the wellbore wall that is broadly aligned with the maximum far field stress. Except with the strongest and stiffest rocks, the fractures in this region initiate and develop mainly as shears, which contrasts sharply with the received wisdom for what is expected. This response also applies when we impose a stimulation loading inside the wellbore (fluid injection).

M3 - Paper

ER -

Alruwaili K, Couples GD, Ma J. Initiation of Stimulation Treatments Depends on Wellbore Mechanical Responses During Drilling. 2017. Paper presented at SPE EUROPEC 2017 at the 79th EAGE Conference and Exhibition, Paris, France.