Session 9

Thursday, December 8th

8:00am – 9:00am US Central Time

Presentation 1: 08:00 AM 

Stress Testing – Measuring Insitu Stress 
Speaker: Emilie Peyret (Schlumberger)

Emilie Peyret is a Reservoir Domain Champion at Schlumberger, with a diverse experience in wireline formation testing and sampling and stress testing. She has worked in Kuwait, Mexico, Central and West Africa, and Europe.

Abstract : Stress testing or micro hydraulic fracturing measures minimum horizontal stress insitu at a specific depth. A direct measurement of the minimum horizontal stress of the cap rock relates directly to the maximum safe injection pressure that can be used in the reservoir layers below said cap rock or it can directly impact production, and/or the amount of fluid that can be stored in an underground storage. This measurement is a calibration point for the geomechanical models, reducing uncertainty that exists, and derisking the reservoirs and projects.

Characterizing the current state of stresses with a formation tester over a caprock and a reservoir or even over an entire lithological column is becoming more in demand with the increase in storage projects and the energy transition underway. The complexity of the formations to be tested, from deeper, harder rocks, to tighter more impermeable formations such as caprocks means that new workflows need to be built to maximize data accuracy as well as efficiency.

Current day stress testing capabilities and improvements in the hardware will be discussed as well as different methods available to evaluate tight formations in order to estimate closure stress.

Presentation 2: 08:30 AM

Successful Cap Rock Stress Testing with a Wireline Straddle Packer Tool Configured with an Innovative Controlled Pressure Bleed Off Design
Olav-Magnar Nes, Egil Romsås Fjeldberg, Nils-André Aarseth – Aker BP, Bob Engelman, Venkat Jambunathan, Michael Evans, Tony van Zuilekom - Halliburton

Speaker: Olav-Magnar Nes, Aker BP

Abstract: Knowledge of the minimum principal stress in the overburden is highly valuable – and even required – for well design, drilling, completion, plug and abandonment, and reservoir injection planning optimization. Access to an effective methodology whereby the stress could in principle be reliably determined at multiple arbitrary depths along the wellbore throughout the overburden is thus highly beneficial to more reliably predict the in-situ stress state.

Within the reservoir, such data have been successfully acquired using straddle packer wireline tools, the so-called microfrac test. However, shaly overburden and cap rock formations in particular have very low mobility, therefore the induced fracture bleeds off at an extremely low rate after shut-in. This lack of formation leak-off and fracture closure renders least principal stress analysis difficult without a controlled pressure release option including sufficient volume control.

The recent deployment of new technology enables microfrac tests to be successfully applied to tight formations. A new flow-back option has been deployed and utilizes the injection pump in reverse mode as a fluid expander which moves fluid from high to low pressure. Fluid injected into the fracture flows back to the borehole at a controlled rate, enabling high quality tight formation stress testing. A description of the new method and the first field implementation, which turned out to be a success case where data were acquired at multiple depths in a well on the Norwegian Continental Shelf (NCS), is given. The subsequent application of the results in terms of constraining the minimum horizontal stress and pore pressure models for the well is presented, illustrating the value of the tool and the microfrac stress data.

Olav-Magnar Nesis Senior Drilling Engineer Rock Mechanics at AkerBP in Trondheim. He has a PhD in solid state physics from the Norwegian Institute of Science and Technology in Trondheim, NTH (now NTNU), in 1992. He joined SINTEF Petroleum Research in 1992 and AkerBP in 2013. His general interests are within rock mechanics and rock physics. He has extensive experience with in-situ stress testing and has been actively involved in development and improvement of methodologies for acquiring microfrac stress data in tight formations.

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