The authors formulated and described problem associated with reducing horizontal well productivity during the bringing the well on to stable production on the field with high-viscosity oil and unconsolidated sandstones. Optimization solutions are applied for the program of well output to the target bottomhole pressure. After productivity analysis of the first wells drilled during full-scale development of the reservoir it was concluded to use filters with a long interval of winding. Based on additional laboratory experiments the composition of the drilling mud was changed and it was decided to use breaker system as replacement fluid after drilling. Bench testing of downhole filters showed that destruction of rocks forms so-called ‘pillow’ on the filter that significantly reduces the rate of oil through the filter element. This happens due to the adhesion of mixture of shattered rocks and high-viscosity oil on the filter which in turn leads to lower productivity of wells.
After analyzing the dynamics of bottom hole pressure in the wells it was determined that the most likely reason for the extra decline in productivity of wells is the intensity of the decrease of bottomhole pressure at an early transient regime of filtration which leads to significant gradients of pressure in the bottomhole zone of the well and subsequent destruction of the rock. According to the laboratory test results of core analysis and geomechanical modeling it was determined that the discreteness of the decrease of bottomhole pressure up to 0.5 MPa allows to bottom-hole formation zone to be resistant to deformation and destruction. In accordance with it the step of reduction of the bottomhole pressure at the output wells on production regime was chosen to be 0.3-0.5 MPa.
Thus during full-scale development it was recommended to include constraints on the bottomhole pressure decrease in time, the control of suspended solids concentration, the dynamic level, the performance of the pump during the transition to the next level of reduction in bottomhole pressure.
References
1. Research report “Tekhnologicheskaya skhema razrabotki Vostochno-Messoyakhskogo neftegazokondensatnogo mestorozhdeniya” (Technological scheme for the development of the East Messoyakh oil and gas condensate field), Part 4, Tyumen': Publ. of Gazpromneft' NTTs, 2014.
2. Research report “Potokovye eksperimenty na obraztsakh kerna skvazhin Vostochno-Messoyakhskogo mestorozhdeniya” (Stream experiments on core samples of the East Messoyakhskoye field), Tyumen': Publ. of Neftekom, 2014, 311 p.
3. Zoback M.D., Reservoir geomechanics, Cambridge: Cambridge University, 2007, 505 p.
