CHALLENGE ■ Remodel South Swan Hills—a giant

mature carbonate atoll field—to estimate remaining OIP

■ Characterize stratigraphically trapped oil

SOLUTION ■ Field remodeled in the Petrel*

E&P software platform ■ Facies relationships determined ■ Volumetric calculation run and tested;

static model selected from sensitivity analysis

■ Remaining OIP simulated

RESULTSAs a result of the project, Penn West Exploration achieved the following:

■ Determined the geology of the South Swan Hills field

■ Clarified which factors controlled the remaining OIP

■ Increased original OIP estimates by 18%

■ Instigated new horizontal drilling plans

The South Swan Hills reservoir is a giant Devonian carbonate play in Alberta, Canada. It is one of many large atoll buildups that developed within the extensive reef systems in this area.

Reserves estimation for the South Swan Hills field was historically undertaken using traditional 2D mapping methods. The oil in place (OIP) was calculated at 950 MMbbl. The field underwent extensive waterflooding in the 1960s and 1970s, followed by hydrocarbon miscible flooding in the 1980s and 1990s. Believing that a combination of horizontal drilling, multistage fracturing, and enhanced oil recovery methods could improve recovery from this large and mature oilfield, Penn West Exploration sought to remodel the reservoir to more accurately predict its production potential.

Model buildingThe oil is stratigraphically trapped within the reef, so a detailed understanding of its carbonate facies relationships is important for success. Penn West Exploration geologists worked in collaboration with Schlumberger to remodel the field using the Petrel E&P software platform. Due to their influence over other petrophysical factors, the main objective was to gain a better understanding of the facies relationships.

A structural framework was built to accurately characterize the reef cycles—it was critical to represent these reservoir units accurately in 3D, as they each have different depositional characteristics. Controlling the various facies proportions within each of the units presented a challenge, however. To overcome this, the team used Petrel data-analysis tools for a better understanding of the proportions of each well’s facies code. They then mapped these into probabilities, using a convergent algorithm within the Petrel mapping module. The ability to control the modeling by facies code—and stratigraphic unit—using the facies-modeling process in the Petrel platform allowed for a geologically accurate 3D representation to drive the rest of the modeling workflow.

CASE STUDY

Reservoir Simulation

Bivariate transforms for petrophysical modeling.

Penn West Exploration Revives Mature Carbonate Field—Original OIP Estimates Increase by 18%Petrel E&P software platform instrumental to new field planning

The final static model was chosen from the P50 result of the uncertainty run, which had similar average porosity and permeability as the original interpretations from the 1950s. This model predicted 1,129 MMbbl of original OIP for the South Swan Hills Unit, which is an 18% increase when compared with previous estimates.

Penn West Exploration was able to simulate and match the South Swan Hills field against historical production data. With a good well-by-well history match, the team plans to embark on horizontal well planning, aiming to maximize the economic oil recovery of this huge resource.

E-mail sisinfo@slb.com or contact your local Schlumberger representative to learn more.

The porosity was modeled biased to the facies distribution related to the depositional characteristics of the field. A correlation was observed between the porosities and the permeabilities at the wells, so a bivariate transform was used as part of the Gaussian random function simulation algorithm. This provided a specific range of permeabilities for each porosity value—a more realistic approach than simply assuming a linear relationship.

Better insight, increased OIP Once the model was complete, the team was able to run a volumetric calculation. To test the results and determine which parameters most affected the model, an uncertainty analysis was also run. The Petrel platform allowed the team to run 1,200 realizations of the model in a short timeframe, adjusting saturation, fluid contact, and seed numbers.

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*Mark of Schlumberger Other company, product, and service names are the properties of their respective owners.Copyright © 2012 Schlumberger. All rights reserved. 12-IS-0360

CASE STUDY: Petrel E&P software platform instrumental to new field planning in Alberta, Canada

Facies distribution based on probability analysis.

Reef build up modeled in 3D.

“The ability to accurately model in 3D—and test different scenarios—led to a huge increase in the OIP estimates and drove new drilling plans.”

Hadi Slayman Senior Geologist

Penn West

”Controlling the facies model on a unit basis—with integrated data analysis—helped us get a handle on the geology of this field, and understand which factors were controlling the OIP.”

Stephen Longfield Geologist

Penn West Exploration