Seismic Uncertainties and Their Impact (SEG SRW 2013)

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SEG 2013 Summer Research Workshop
Date 8-12 July 2013
Sponsor(s) Schlumberger
Location Rimrock Resort Hotel, Banff, Alberta, Canada

Seismic Uncertainties and Their Impact

Uncertainty plays a very important role in managing risk at all stages of the exploration and production (E&P) business. Much of this uncertainty is tied to the imperfect description of the subsurface in terms of structure and formation properties (the earth model). Therefore, our ability to better understand and quantify the uncertainties in this model will help better manage the risk and reduce cost in our industry. In this multidisciplinary workshop we discussed the root causes of this uncertainty, how we quantify it, how we can reduce it, and what it means to the users of the earth model in other disciplines including drilling and production.

Seismic plays a central role in creating the earth model. Subsurface structural model is obtained by interpretation of depth migrated seismic images. Formation properties such as velocity, density, lithology, pressure, porosity, and pore fluids are obtained by advanced processing of seismic data calibrated by well information. Consequently, it is key to understand what types of uncertainties are introduced in this seismic model generation process and how we can quantify them. This understanding facilitates creation of new techniques and establishment of best practices for accurate characterization of uncertainties, leading to improved risk management. Several sessions were held to discuss new advances in model uncertainty analysis and quantification.

The real impact of earth model uncertainty is measured by how it influences decision making at various phases of E&P activities including:

  • Exploration
  • Drilling
  • Reservoir management
  • Recovery optimization
  • Health and environment

Presentations were given by industry experts in these areas and discussion sessions with the objective of building a bridge between the seismic model builders and the users of these models.

Schedule and Session Descriptions

The workshop began on Monday evening, 8 July, with a welcome reception at the hotel. A welcome and keynote speaker began the morning on Tuesday, 9 July, and the remainder of the day featured presentations on seismic uncertainty (Paul Williamson, Konstantin Osypov, Session Chairs).

The Uncertainty Sessions focused on the fundamentals of the uncertainty in seismic imaging and characterization. Examples are: limitations in the precision of measurements (S/N) and acquisition geometries; types of uncertainty, such as kinematic vs. dynamic; and approaches for estimating output uncertainties from these inputs. It also featured contributions addressing statistical models of earth parameters and the choice of parametrization, the definition and use of prior models, and the distinction between uncertainty and bias, due (for example) to the neglect of some aspects of the physics in the model such as elasticity, attenuation or anisotropy.

Tuesday Sessions included a Mixed Posters Session.

Wednesday Morning Sessions focused on seismic uncertainty's Impact on Exploration (Frederik Pivot Session Chair) This session included papers focusing, for example, on how seismic uncertainties are taken into account for interpretation (horizons and faults that define the envelope of potential prospects) and how they are finally integrated for estimating ranges of possible volumes for Hc in place. Papers also showed impact on relevant exploration attributes like coherency, seismic impedances, avo cubes, and case studies showing pitfalls, and propositions about more "uncertainty-proof" prospect interpretation workflows.

Wednesday afternoon included time off to take part in planned activities or to just enjoy the beautiful scenery and cool mountain air.

The Thursday Morning Session looked at the Impact on Drilling (Cengiz Esmersoy, Session Chair) of seismic uncertainties. Uncertainties in structural images, drilling target locations, and formation properties such as pore pressure could result in unexpected hazards and increased costs. Impact of these on drilling risk management was discussed.

Thursday Afternoon Sessions examined the Impact on the Static Reservoir Model (Cory Hoelting, Session Chair). This session included papers and discussion on how seismic uncertainties are taken into account when building P10, P50, P90 (or high, mid, low) geomodels. They focused on relevant aspects of static modeling, including but not limited to: impacts on the geometry (and gross rock volume) of the model; stochastic specification of reservoir properties populating the model, and how the standard base case workflow is modified to create end-member models.

On Thursday evening, attendees enjoyed a group dinner.

Friday Morning's Session looked at the seismic uncertainties Impact on Production (Mike King, Session Chair) This session considered the interaction between reservoir uncertainties, multiple models of the reservoir, reservoir management and surveillance and production optimization. As we develop a reservoir we produce oil and gas but also acquire dynamic data about the reservoir. The workshop focused especially on presentations describing the change in uncertainty (collapse or expansion), and integrating it into decisions on well placement and/or well optimization during field development.

The workshop concluded on Friday at noon.

Schlumberger

Organizing committee

Cengiz Esmersoy, Chairman (SLB)
Cory Hoelting (Chevron)
Fredrik Pivot (Total)
Mike King (Texas A&M University)
Konstantin Osypov (SLB)
Michel Verliac (SLB)
Paul Williamson (Total)

External links

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