Predicting Openhole Horizontal Completion Success on the North Slope of Alaska

Erwin, Michael; Ogbe, D.O.

doi:10.2118/97121-ms

“…Some important parameters for selecting this kind of completion are wellbore stability, geological properties, and reservoir fluids control, as defined by hydraulic units and permeability magnitudes and anisotropy 35 . Some important parameters for selecting this kind of completion are wellbore stability, geological properties, and reservoir fluids control, as defined by hydraulic units and permeability magnitudes and anisotropy 35 .…”

Section: New Completion In Openhole or Noncemented Linermentioning

confidence: 99%

Horizontal Well Completion and Stimulation Techniques--A Review With Emphasis on Low-Permeability Carbonates

Rodrigues

¹

,

Neumann

²

,

Torres

³

et al. 2007

Proceedings of Latin American &Amp; Caribbean Petroleum Engineering Conference

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fax 01-972-952-9435. AbstractThis paper presents a brief review of the available techniques in the oil and gas industry to complete and stimulate horizontal wells, with emphasis on low permeability carbonates. These techniques can also be applied in non-conventional reservoirs, particularly in tight formations. The paper starts by reviewing the lessons learned in some chalk fields in the North Sea (Dan, Halfdan, South Arne, Valhall and Eldfisk) and in a few pilot projects offshore Brazil (Congro and Enchova). Based on these lessons learned and in the broad literature, the paper devises some considerations on the methodology to select completion and stimulation techniques for horizontal wells. Cased and cemented horizontal wells, in addition to open hole and perforated/slotted liners wells are addressed. The macro aspects of field/area management are stressed as the completion and stimulation drivers. The key parameters for designing, implementing and evaluating horizontal completion and stimulation are presented, emphasizing the most common failures and the controversial aspects. The paper presents a summary of mature field and new scenarios that are candidate to horizontal completion and stimulation in Brazil and other Latin America countries. Then it makes a few comments on the resources available in Latin America to face the mentioned opportunities and related challenges. It is supposed that this brief review will be useful for the low permeability scenarios in Latin America and worldwide. Completion and Stimulation of North Sea Low-Permeability CarbonatesThe North Sea low permeability chalks are taken here as a reference due to the outstanding technological evolution verified there in the last decades. Amongst more than ten fields producing from these reservoirs in the North Sea this paper focuses on the Dan, Halfdan, South Arne, Valhall and Eldfisk fields. The main characteristics of these fields are: shallow waters (43 to 69 m), dry completion, high volumes of OOIP (1.6 to 2.9 billions barrel), low permeability carbonates (0.2 md to 10 md) with microfractures in the central areas (10 md to 120 md), high porosities (up to 48%), soft to very soft chalks, small to medium net pays (15 m to 65 m), high oil saturation (up to 97%), and light oils ( about 36 o API). What most distinguishes these fields is their over-pressured soft chalks which are subjected to a high degree of compaction under pore pressure depletion, resulting in loss of drilling fluids, rapid production decline, well failures and seafloor subsidence. On the other hand the positive effects of rock compaction as a reservoir drive energy, outweigh by far the negative ones. The recovery factor under primary recovery can be as high as 30%. In general the North Sea chalks experienced an evolution from vertical/directional wells stimulated with acid treatments to multiple fractured horizontal wells.

show abstract

Horizontal Well Completion and Stimulation Techniques—A Review With Emphasis on Low-Permeability Carbonates

Rodrigues

¹

,

Neumann

²

,

Torres

³

et al. 2007

Latin American &Amp; Caribbean Petroleum Engineering Conference

View full text Add to dashboard Cite

fax 01-972-952-9435. AbstractThis paper presents a brief review of the available techniques in the oil and gas industry to complete and stimulate horizontal wells, with emphasis on low permeability carbonates. These techniques can also be applied in non-conventional reservoirs, particularly in tight formations. The paper starts by reviewing the lessons learned in some chalk fields in the North Sea (Dan, Halfdan, South Arne, Valhall and Eldfisk) and in a few pilot projects offshore Brazil (Congro and Enchova). Based on these lessons learned and in the broad literature, the paper devises some considerations on the methodology to select completion and stimulation techniques for horizontal wells. Cased and cemented horizontal wells, in addition to open hole and perforated/slotted liners wells are addressed. The macro aspects of field/area management are stressed as the completion and stimulation drivers. The key parameters for designing, implementing and evaluating horizontal completion and stimulation are presented, emphasizing the most common failures and the controversial aspects. The paper presents a summary of mature field and new scenarios that are candidate to horizontal completion and stimulation in Brazil and other Latin America countries. Then it makes a few comments on the resources available in Latin America to face the mentioned opportunities and related challenges. It is supposed that this brief review will be useful for the low permeability scenarios in Latin America and worldwide. Completion and Stimulation of North Sea Low-Permeability CarbonatesThe North Sea low permeability chalks are taken here as a reference due to the outstanding technological evolution verified there in the last decades. Amongst more than ten fields producing from these reservoirs in the North Sea this paper focuses on the Dan, Halfdan, South Arne, Valhall and Eldfisk fields. The main characteristics of these fields are: shallow waters (43 to 69 m), dry completion, high volumes of OOIP (1.6 to 2.9 billions barrel), low permeability carbonates (0.2 md to 10 md) with microfractures in the central areas (10 md to 120 md), high porosities (up to 48%), soft to very soft chalks, small to medium net pays (15 m to 65 m), high oil saturation (up to 97%), and light oils ( about 36 o API). What most distinguishes these fields is their over-pressured soft chalks which are subjected to a high degree of compaction under pore pressure depletion, resulting in loss of drilling fluids, rapid production decline, well failures and seafloor subsidence. On the other hand the positive effects of rock compaction as a reservoir drive energy, outweigh by far the negative ones. The recovery factor under primary recovery can be as high as 30%. In general the North Sea chalks experienced an evolution from vertical/directional wells stimulated with acid treatments to multiple fractured horizontal wells.

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Wellbore Stability Model for Standalone Liner Completed Wells in Carbonate Reservoirs Subjected to Acidizing Jobs – II. Wellbore Stability Simulator

Santos

¹

,

Ferreira

²

2015

Day 1 Tue, October 27, 2015

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Mechanical stability analyses are mandatory to identify suitable candidates for openhole completions. These analyses should comprehend the effects of production drawdown and reservoir depletion state anticipated by the production plan. The understanding and modeling of the physico-chemical interactions between rock and flown fluids and their impacts on the rock mechanical properties have been presented in a companion paper. This paper introduces the three methodologies intended for the wellbore stability analyses, namely the i) elastic analytical; the ii) empirical solids production and the iii) 2D elastoplastic finite element simulator (FE) and describes the reasons two of them have failed to incorporate the dissolution-induced rock weakening effects on the wellbore stability. The resulting numerical model has been implemented as a standalone specialist 2D FE Simulator. The simulator provides the well design engineers a user-friendly interface upon which they can evaluate the effects of the wellbore and reservoir pressure changes, as well as the aforementioned rock weakening effects from an acidizing job, on the wellbore stability. The mechanical wellbore response presented by the simulator elucidates how the stress and strain patterns change after an acid well stimulation job. Wellbores under virgin rock conditions tend to fail by localized plastified zones, also referred to as breakouts, whereas wells subjected to acidizing jobs present extensive straining due to rock weakening. The boundaries of the acidized zone encloses a much less rigid rock prone to deform and compact. On one side this compliant zone provides a gradual shear distribution along the well radius inside the formation and mechanical confinement to the surrounding intact rock and therefore helps this rock in supporting the stresses as if the wellbore were much larger. However, on the other side this significant weakened rock volume poses uncertainties about its own stability or solids production risks. The installation of a perforated or slotted liner/casing acting as a bearing element tends to hold this compliant material back and accounts for the material uncertainties and lack of model representativeness in terms of eventual preferential dissolution patterns. The unprecedented results presented by the developed simulator are assisting the company on the standalone completion decisions and increasing the robustness of well completion designs, therefore assuring the perennity of the CAPEX.

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Predicting Openhole Horizontal Completion Success on the North Slope of Alaska

Cited by 3 publications

References 29 publications

Horizontal Well Completion and Stimulation Techniques--A Review With Emphasis on Low-Permeability Carbonates

Horizontal Well Completion and Stimulation Techniques--A Review With Emphasis on Low-Permeability Carbonates

Horizontal Well Completion and Stimulation Techniques—A Review With Emphasis on Low-Permeability Carbonates

Wellbore Stability Model for Standalone Liner Completed Wells in Carbonate Reservoirs Subjected to Acidizing Jobs – II. Wellbore Stability Simulator

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