Geomodelling and Well Architecture, Key Issues to Sustainable Reservoir Development

Abstract

Three-dimensional modelling of geologic structures is routinely applied in petroleum and, at a lesser extent though, in geothermal engineering and has proven an efficient tool in investigating complex tectonic and lithological environments. In geothermal development it is often utilised for 3D temperature modelling and well siting, the latter in conjunction with 3D seismic surveys, purposes. Well architecture, contrary to oil and gas drilling practice, has not yet passed the (slightly) deviated well design stage aimed at securing larger production vs injection well downhole spacings and intercepting productive fractures wherever they develop (sub) vertically. The present work was assigned a three fold objective (i) comprehend and properly assess a relevant multilayered structure from, log issued, well fingered data and derive reliable interpolation guidelines for further reservoir simulation studies, (ii) maximize deliverabilities of geothermal district heating production/injection well arrays, and, last but not least, (iii) minimize thermal breakthroughs thus extending reservoir life and achieving sustainable reservoir management targets. Geomodelling has been implemented on a selected Paris Basin area by integrating local geothermal and hydrocarbon lithological, logging and testing data. Horizontal and multilateral well designs have been modelled and the impact of these unconventional (geothermally speaking) architectures appraised in terms of deliverabilities, bottomhole streamline/pressure/temperature patterns and ultimately breakthrough transients. The exercise proved rewarding in (i) validating the geomodelling approach, with respect to its input to an improved conceptual model and reliable predictive hydrothermal simulations, and (ii) securing well/reservoir longevities by designing either horizontal or multilateral well paths, depending upon local reservoir layering, best assessed by combining geomodelling and logging while drilling.