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Need
Status: Need is Closed

Innovative and cost-efficient downhole stress measurement methods

Request Number

NG_2018_0076_N_002
Point of Contact
Need was closed on
May 22
Description

We are looking for solutions, methods and/or technologies which can:

 

  1. Improve the existing procedures / methods to measure formation pore pressures
  2. Enable real-time -  continuous or intermittent - determination of the minimum formation stress while drilling
  • Brief interruptions of the ongoing operation to acquire measurements are acceptable

 

We are primarily looking for a solution which does not involve actual fracturing of the formation but where the formation stress is estimated from “log” measurements.

 

Background

Within hydrocarbon containing formations the fluids within the pore space or the available space in fractures or cavities of the reservoir rock are under pressure (= “pore pressure”).

 

When a well is drilled into a formation, stressed solid material is removed. The borehole wall is then supported only by the fluid pressure (termed "mud weight") in the hole. The drilling mud has many functions including pressure control, wellbore stabilization, transport of cuttings to the surface, cooling and lubrication of the drill bit and as data transmission medium. The mud weight needs to give good control of formation pressures and wellbore stability without risking that the formation itself is fractured and the well goes on losses. This “lost circulation pressure” or “fracture gradient” is an important parameter for well design and it’s estimation for a priori and during the actual drilling progress is important.

 

Figure 1

 

The difference between the pore pressure and the fracturing pressure defines the mud weights that can be used during drilling. This ‘drilling window’ in Figure 1 shows that the mud weight must exceed the pore pressure but should also stay below the fracturing pressure. We use the term fracturing pressure/gradient here with the understanding that lost circulation can also be triggered by mechanisms other than induced fracturing at the wellbore.

 

The operational drilling window in the reservoir and near overburden will vary throughout a well’s life as a response to pore pressure and temperature changes caused by the extraction of the hydrocarbon fluids (Figure 2).

 

Figure 2

 

The ability to drill safely and efficiently  in depleted reservoirs is important for achieving goals for oil and gas recovery.  However, drilling and completing new wells in a depleted reservoir may be challenging since changes in the drilling window that arise from changes in pore pressure and stresses can be difficult to predict especially in layered reservoirs with different lithologies, differential depletion and where loss incidents may not be caused solely from fracture events.

 

Statoil is interested to get in touch with those having methods or able to propose innovative approaches to get to a better understanding of pressure profiles of complex and partially depleted reservoirs. Preferred methods will allow open-hole measurements or need only a limited amount of interruption of the drilling operation.

Key success Criteria
  • Preferably no need to shut in the well (“open hole measurement”)
  • Data can be transferred via telemetry and/or memory recording
  • Measure pressures from 1,000 Psi to 10,000 Psi with an accuracy of 10%
  • Able to withstand high temperatures (typical temperatures in wells are around 80 to 150°C with higher possible up to 250°C)
  • Do not pose HSE hazards to operators e.g. not make use of radioactive sources, hazardous chemicals, explosives

 

Possible Approaches
  • Improved direct pressure measurements methods
  • Measuring the ultrasound response to the surrounding pressure
  • Electrical resistivity based methods
  • Quartz gauge designs
  • Methods based on the relation between effective stress and porosity (e.g. ‘Terzhagi theory’)
  • Innovative indirect methods like determination of the ‘Eaton Ratio’ and ‘Equivalent Depth’ method

 

Approaches not of Interest
  • Fracturing of formation
  • Extended Leak-off tests
  • Radioactive sources, hazardous chemicals, explosives

 

Due Date
Feb 15
Items to be submitted
  • Non-Confidential description of technology, method or equipment
    • Working principle
    • Supporting data or technical rationale for conceptual approaches
    • Technology maturity (concept, lab-scale, ready to scale up, suitable for practical use)
  • Estimated developments requirements e.g. modelling, prototype testing, field trials… including timing and estimated budget
  • Intellectual property status
  • Expertise of proposer in this or related fields

 

Gallery Moderator(s)
Jos Cenens
Request Number
NG_2018_0076_N_002
Preferred Collaboration Types
Area of Interest