Mapping Reservoir Volume Changes During Cyclic Steam Stimulation Using Tiltmeter-Based Surface-Deformation Measurements

摘要

Surface deformation measurements have been used forrnyears in oilfields to monitor production, waterflooding, wasterninjection, steam flooding, and Cyclic Steam Stimulationrn(CSS). They have been proven to be a very effective way tornmonitor the field operations and save money for operatorsrnwishing to avoid unwanted surface breeches, casing failuresrnand excessive subsidence due to production. This paperrndemonstrates that more information can be extracted fromrnsurface deformation measurements by inverting the surfacerndeformation for the volumetric deformation at the reservoirrnlevel, so the aerial distribution of volumetric deformation canrnbe identified. First, a poroelastic model is presented torncalculate the deformation due to the volumetric change in thernreservoir. Then, a linear geophysical model is formulated torninvert for the reservoir volumetric deformation from thernmeasured surface deformation (or tilt). Constraints are addedrninto the procedure as necessary to better resolve the inversionrnproblem. After each inversion, the theoretical surfacerndeformation (displacement, tilt, reservoir compaction andrnvolumetric strain) can be calculated from the invertedrnvolumetric deformation distribution which best fits thernmeasured deformation data (or tilt) at the surface. Therntechnique of mapping fluid flow using surface deformationrnwas applied to real data from a cyclic steam injection project.