Is Geomechanics the essential basis for physical understanding of Rock Deformation, Natural Fracture Systems and Flow Responses in Hydrocarbon Reservoirs?

Workshop 5: Sunday, 2 June
Conveners: Abdullah Subaie (Saudi Aramco)
Khalid Hawas (Saudi Aramco)
Gary Couples (Heriot-Watt University)

The majority of the remaining oil and gas in the Middle East, 70% of the world’s producing fields, are hosted in carbonate reservoirs, with fractures contributing to their heterogeneity and complexity. Hence, there are increasing technical challenges in continuing to exploit such accumulations. Geomechanics provides physical understanding of processes relating to: the origin and distribution of fractures, their role in fluid flow, and impacts in the near-well region. This workshop explores the value of geomechanical considerations in the prediction of natural fracture patterns and the use of that information in reservoir-performance approaches. 

Description: 

Naturally-fractured reservoirs occur in almost all hydrocarbon systems, and this may be the dominant reservoir type in many settings. Carbonate reservoirs commonly show the effects of fractures, but fractures also play important roles in basement fields, in silici-clastics, and in unconventionals, where stimulation aims to create new fractures as well as provoking movements on pre-existing natural ones. In all of these situations, the existence of fractures (natural and newly-created) presents the potential (or likelihood) of altering the way that the reservoir behaves – pushing the responses away from the smooth characteristics expected of a simple continuum. 

We can homogenise the fracture-governed behaviors into a continuum-equivalent upscaled response, and that is what is used to perform reservoir-scale simulations. But we struggle to down-scale a continuum-equivalent response so that we can understand the local roles of fracture distributions, mechanical state alterations, and the impacts of fluid injection/production (with possible thermal effects). The technical (and conceptual) challenges are pushing us towards adopting a multi-scale approach – both in our understanding, and when performing numerical simulations. This ‘revolution’ in fractured-reservoir approaches is underway, although it is an almost-silent revolution because the critical action is occurring on deep technical levels that may not make it onto the radars of many who will ultimately be affected. 

In this Workshop, we will expose the important technical concepts that are emerging, and which will become critical features of future workflows. We also aim to re-assure everyone of the continuing important role for observation-based characterization of fracture distributions, as these provide the only independent constraining data. The over-riding goal is, as always, and as will always be, to provide the best-possible predictions of fractured-reservoir performance to underpin operational decisions. Because the physics within fractured reservoirs is so dependent on the role of the discontinuities, the achievement of ‘best possible’ outcomes demands comprehension by both non-specialists as well as the experts. This Workshop examines how we need to improve the communications and understanding that is demanded of all participants. 

The workshop will be kicked off by a keynote speaker covering the essential elements in characterization and building fully-coupled geomechanical models from static, 3D seismic and dynamic datasets for prediction of fractured reservoir behavior. 

The workshop consists of 5 sessions: 

  • Session 1: What does it take to build a fully-coupled geomechanical model, and what are the associated challenges? How necessary is it to have a fully-coupled model? What simplifications are warranted, and when? 
  • Session 2: How can we better use seismic for predicting/characterizing fractures away from wellbores? Or for deriving estimates of physical states in the inter-well regions? Do the models, which relate fractures to seismic effects, have enough of the right physics in them? 
  • Session 3: What are the key datasets obtained from drilling and production data to aid us in building fracture models? What are the discriminating data, and which data are less informative? Are there significant differences between geostatistics-based fracture-distribution models, and those which apply stochastic methods to process-rooted conceptual distributions? 
  • Session 4: Do we have enough resources, and are we competent enough to build geomechanically-constrained models? Are we competent enough to use them effectively? What training is needed? What ‘cultural’ changes do we need to accomplish? What factors limit the present benefit/cost ratio of adding serious geomechanics into the workflow? 
  • Session 5: Breakout sessions to brainstorm these topics, aiming to derive a statement about the present and future status of geomechanics use in fractured reservoirs. They also seek to identify what current information types give the most value towards answering the operational questions that arise in fractured reservoirs. The sessions are based around the concept of applying financial resources (a budget!) to create the solutions to the outstanding questions. 
Participants from operators, service companies and academia are encouraged to contribute to make the most out of the workshop.

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