A stimulation test using electric heating was conducted on a single oilproduction well in the Schoonebeek reservoir in The Netherlands during 1989 and1990. The performance of the test and its interpretation is described.
The Bentheim reservoir sands are 31 m thick with a porosity of 0.3 and apermeability in the range 0.2 - 4 µm2; the oil has an in-situviscosity at 160 mPa.s and is waxy with a cloud point very close to thereservoir temperature of 40 °C. The reservoir pressure of about 7000 kPa issupported by a strong edge aquifer. The objective of the test was to stimulateoil production with heat and, particularly, to melt wax that was suspected tobe present either near the wellbore or uniformly throughout thereservoir.
Prior to stimulation the oil production rate was 13 m3/d at a watercut of 35%. As the surface power dissipated was increased above 60 kW, the oilproduction rate increased abruptly to 30 m3/d with a bottomholetemperature in the range 54 to 60 °C; at higher power levels no furtherincrease of production rate was observed.
Analytical methods proved very useful for understanding the electric healingprocess, particularly for tracing the electric current flow path in thereservoir and for modelling the heat distribution and production response.Numerical simulations of the well's performance showed that the observed abruptincrease of oil production rate was compatible with the melting 01 wax at 60 °Cand partial removal of a skin (of approximately 27) but not of a wax depositeduniformly throughout the reservoir.
Though electrical heating has been used to stimulate well productivity alvarious times over the last 25 years, it is not widely applied. A lest of thestimulation method was recently completed on Well SCH-280 in the RW2-E area ofthe Schoonebeek oil reservoir of The Netherlands (see Figs. 1 and 2) by the Nederlandse Aardolle Maatschappij B. V. (NAM). In this paper we describe theproperties of the Schoonebeek reservoirand the characteristics of Well SCH-280and review the objectives, test programme and actual performance of theelectric heating stimulation (EHS) test. In several respects, the informationrequired to interpret the test unambiguously was not available. To circumventthese limitations, methods were developed for inferring the electric currentflow path and heat distribution in the reservoir, Using both analytical andnumerical simulation methods, a broadly consistent interpretation of the testwas developed and this is described herein.
Over the last 25 years there have been a number of reports in the literature ofplanned or executed field tests of the electric heating process, mostly basedon the ohmic dissipation of electric energy in the formation. Electrothermic Co., for example, stimulated four wells of the Little Tom field in South Texas.The reservoir there contains 8 - 12 °API gravity oil with a high pour point[1,2].