Subsurface Integration: Take it or Lean it!

Subsurface integration has always been a hot topic for the EP companies. Today, more than ever, there is a strong push to tackle the subsurface challenges in an integrated fashion. Unfortunately, the misconception of collocating subsurface people in the same corridor as the one and only requirement to achieve subsurface integration is well alive.

Subsurface integration, put in simple words, is looking at the subsurface object from different angles (the subsurface disciplines) to ensure no stones are left unturned. The key is to find answers and remove as many question marks as possible on the understanding of the reservoir. Taking the example of a classical reservoir modelling exercise (from inputs to forecast), four levels of subsurface integration can be distinguished:

Level 0: Disintegration (no integration)

The reservoir model is built upon subtasks that are done in isolation and not contemporary each other’s. A good example would be a legacy seismic interpretation performed several years prior to the petrophysical interpretation. The conceptual ideas used for the static model takes all those inputs and simply “plug” them in the geomodelling software without further attempt to decipher the subsurface and identify trends.

Level 1: Proto integration

The infamous “throw over the fence” culture. All the subsurface building blocks are put in place sequentially, QC’ed and handed over to the next link in the chain. The textbook example is the seismic and the petrophysical interpretation performed concurrently. The resulting inputs are approved by the technical authorities and handed over to the Geomodeller. Once the static model is built, it is handed over to the reservoir engineer for history match/forecasting purpose. Often at that stage, significant changes are required to reconstruct a dynamic signal matching the production data. There is no turn back in the sequence and the reservoir engineer is left alone to get the match. I have personally observed some instances where permeability multiplication by several folds and porosity increase by 5 p.u., in total contradiction with the data, where necessary to approach near a history match state.

Level 2: Pseudo integration

The system in place allows some feedbacks to be recycled. Physical collocation between the different subsurface people facilitates communication. A major flaw remains as the work is still done sequentially. If a potential cause of mismatch is identified, another iteration occurs and a new “product” is generated. Although the flexibility is commendable, there is no guarantee of improvement. Worst, this can stretch the overall project timeline and cost valuable extra man hours for potentially no added value.

At this stage, from level 0 to level 3, the reservoir modelling exercise is a sum of several “sub projects”

Level 3: True integration

From the initial setup, the team is fully aligned on the final objective. Collocation is not just physical but also digital. Every discipline has access to one consolidated database. Integrated sessions become a meaningful medium of exchange where all the different disciplines are constantly looking beyond their borders. All the sub tasks start at the same time. Very early in the workflow, a first pass static model is handed over to the reservoir engineer to establish the simulation workflow and distillate the first critical understandings of the reservoir. Seismic close the loop and petrophysical log QC are performed early in the game and in consultation with the full team. Once the inputs are generated, the Petrophysicist and the Seismic Interpreter stay engaged and contribute to subsurface discussions until the simulation stage. That way, some important aspects such as fault seal or reservoir capillary effect on saturation stay high on the radar and can be debated.

Current state and way forward

While it is easy to out pass level 0, most of the EP companies are often stuck between level 1 (proto integration) and level 2 (pseudo integration).

Having a subsurface team with high interpersonal / technical skills is a sine qua non for achieving true subsurface integration. Corporate culture must encourage and cement the bond between the team members.

Computing capabilities and subsurface software must enable flexibility at the click of a mouse.

Most importantly, workflows, modelling philosophy and paradigm should be challenged to ensure that true subsurface integration transitions from being a mere ambition to a (new?) reality.

If you / your organization would like some advice to achieve true subsurface integration. Get in touch at [email protected], we are happy to share our experiences.

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