Closure of open wellbores in creeping salt sheets

Abstract

Safe exploration and production of pre-salt (or subsalt) hydrocarbons require that drilling operations be optimized. We introduce analytical models of wellbore closure, accounting for variations in both the wellbore net pressure and far-field flow rate of an autochthonous or allochthonous salt sheet penetrated by the wellbore. We demonstrate how closure rates of such a wellbore evolve for increasingly stronger Rankine flow. For high viscosity salt (∼10 18 Pa s) the wellbore closes by a pure sink flow without any Rankine shift from its vertical trajectory path. For low viscosity salt (∼10 16 Pa s) Rankine flow dominates. Wellbore closure in salt sheets may vary within the same wellbore due to differential tectonic creep rates at different depths. Mitigation of wellbore closure by, for example, reaming, jarring, brine solution and thermal control, is most effective if spatial variation in closure rates is understood and quantified. Evaluation of wellbore closure rates due to salt creep should be customarily included in wellbore stability analyses before drilling and during well monitoring.

The Role of Salt Tectonics in the Energy Transition: An Overview and Future Challenges

“…First, improved predictability will be key for the development phase where well design will depend on prognosis of intra-salt heterogeneities that can impact well integrity and safety. Encountering unexpected heterogeneities during drilling can lead to dangerous pressures, washout and loss of circulation, and wells can be damaged by shearing or buckling if directions and rates of salt flow (which occur on human timescales) are incorrectly predicted (e.g., Looff and Rautman, 2010a;Kukla et al, 2011;Weijermars et al, 2013Weijermars et al, , 2014Strozyk, 2017;Warren, 2017) (Figure 7). Second, predicting the likely distribution of heterogeneities in salt stocks can help ensure the safe placement of salt caverns, which ideally will be located in relatively homogeneous halite, where properties and stresses are predictable, and where leakage is less likely (e.g., Koyi, 2001;Gillhaus and Horvath, 2008;Warren, 2016Warren, , 2017Pichat, 2022) (Figure 8).…”

Calculation of Pressure Loss of Two Drilling Muds in Noor Oil Field

“…Also, salt dissolves in water, therefore; the salinity of a water-based mud must be kept near or at saturation to prevent or minimize wellbore enlargement that can lead to bad cementing of the casing and incomplete zonal isolation, (Amer, et al, 2016). Boreholes in salt layers tend to be overbalanced, (Weijermars, et al, 2013). After completing the drilling of this hole, casing is placed and then the process of cementing is done.…”

Long-term cavity closure in non-linear rocks

“…An analytical expression has been developed by which allows to quickly evaluate the instantaneous closure velocity and the time available before the well is too narrow to proceed securely. Since then, increasingly complex models have been used to forecast hole closure in the high pressure, high temperature environment encountered during drilling (Carcione et al, 2006;Fossum and Fredrich, 2007;Hou et al, 2012;Paraschiv-Munteanu and Cristescu, 2001;Weijermars et al, 2013). The challenge, however, of understanding the underlying mechanisms of hole closure and providing the best model for it has remained the same.…”