Optimizing oil production in horizontal wells (water/oil cresting in horizontal wells)

Akangbou, HN

Abstract

In recent years, the application of horizontal wells has been predominant in minimizing cresting scenarios due to significant reservoir exposure of its laterals. Cresting is known to occur in horizontal wells when the pressure drop supersedes the hydrostatic pressure existing between the phases in a typical reservoir. Cresting poses problems such as uneconomic oil production rates due to increasing volumes of effluent(s) (unwanted water and or gas) produced with oil over time as well as the overall recovery efficiency of oil reservoirs.

Production optimization from crest-affected thick- and thin-oil rim homogeneous reservoirs were investigated experimentally by considering the effect of varying the inclined sections of a horizontal well at low angles of inclination (15o-30o), initial surface pressures (-4.351Psig), lateral length in reservoir (lr, = 0.305 m) and oil viscosity (50 cP) on oil recovery, oil produced and cumulative water produced during cresting. A strong bottom aquifer and considerable gas cap were modeled at constant bottom water injection rate of 41.68 cm3/s and at atmospheric pressure (14.7 Psi) respectively. An experimental proactive cresting control technique based on reservoir wettability, gravity segregation and effluent(s) breakthrough times were investigated for cresting control in thick- and thin-oil rim homogeneous reservoirs, using an electromagnetic valve installation. Numerical simulations were considered using Particle Image Velocimetry (PIV) to the determine the velocity of captured water cresting images and Computational Fluid Dynamics (CFD) to validate the oil withdrawal rate, Gas-Oil-Contact (GOC) and Water-Oil-Contact (WOC) by applying boundary conditions from the physical model.

From results of varying the inclined section of the horizontal well, the Short radius wells with 30o angle of inclination and ratio of vertical displacement of the inclined section to reservoir height (Vd/Hr) of 0.079 resulted in 177.75 cm3 increment in oil recovered and reduction in cumulative water produced (258 cm3) at a production time of 300 s in thick-oil rim reservoirs while 250 cm3 increment in oil was observed with 356 cm3 reduction in cumulative water produced at a production time of 495 s in thick-oil rim reservoirs with Vd/Hr, 0.063. Further increment of 108.91 cm3 in oil produced and reduction in cumulative water produced (183.99 cm3), was observed when cresting was controlled proactively in thick-oil rim reservoirs. From varying the inclined section of the horizontal well, increment in oil produced of 163 cm3 and 134 cm3 cumulative reduction in produced water were observed at Vd/Hr equals 0.079 in thin-oil rim reservoirs at a simulation time of 210 s while a lower oil increment of 6.84 cm3 and cumulative water reduction of 10.98 cm3 were observed in thin-oil rim reservoirs when controlled proactively. The over predicted quantitative results as high as 75.06% using the CFD model compared with experimental data were due to two-dimensional (2D) model limitations in porous media as well as the corresponding grain sizes. To exemplify, for WOC the predicted results was about 28.56% compared to experimental data at 4.5 s. The average velocity profile from PIV analysis increased steadily from 0.113 to 2.08E-15 m/s from 10 to 90 s.

Citation

Akangbou, H. Optimizing oil production in horizontal wells (water/oil cresting in horizontal wells). (Thesis). University of Salford

• Thesis Type: Thesis
• Deposit Date: Feb 20, 2018
• Publicly Available Date: Mar 20, 2018
• Award Date: Apr 1, 2017