Using a Dynamic Coupled Well-Reservoir Simulator to Optimize Production of a Horizontal Well in a Thin Oil Rim

Abstract

Stabilization and optimization of production are the key challenges for smart well control. In order to compare the effectiveness of different control strategies, a simulation environment can be used. To study and control the effects of for instance slugging, gas coning and wax deposition, both reservoir dynamics and the dynamics of multi-phase well flow have to be taken into account in such a simulation environment. In this paper we use a dynamic coupled well-reservoir simulator to identify instabilities of a field case and test a control strategy to mitigate gas coning and wax deposition. The dynamic simulation environment has been developed within the research framework of the 'Integrated System Approach Petroleum Production' knowledge center of TNO, TU Delft and Shell. This simulator has been validated with field data of a horizontal well located in a thin oil rim, suffering from gas coning and containing a crude which has a high tendency to wax. With the help of the simulation environment it was possible to understand the production instabilities observed in this well and to determine a control strategy to stabilize and optimize its production. The results of the coupled well-reservoir simulations are presented and the phenomena that are most likely to cause the production instabilities observed in the field are identified. In production optimization the current status is to use separate dynamic well and reservoir models. In case of significant reservoir-well interaction this approach gives a non-realistic production forecast. This project gives a clear indication that, when using a coupled simulation on a real field case, a better understanding of the instabilities and therefore a more accurate production forecast and a better control strategy can be designed. Introduction With increasing knowledge and new technologies more complex reservoirs with respect to location and dimensions can be explored. This brings new challenges in e.g. exploration, drilling and production. Furthermore, existing reservoirs require new insights to be able to increase its ultimate recovery. Dedicated simulation software tools can offer these new insights by helping to understand production instabilities and test new control strategies to avoid them and to optimize production. The field under investigation has most of its wells drilled with long laterals in a thin oil rim, which have a strong tendency to gas-cone. Gas coning is a phenomenon where the gas oil contact of a reservoir slowly moves towards a well as a result of oil drawdown, see Figure 1. At a certain moment in the production life of the well the gas oil contact will reach the well and the well will experience high influx of free gas. A second important issue which is causing production limitations is wax deposition. Wax deposition is a known problem for reservoirs located in cold areas or deep water, but also for reservoirs containing a crude which has a large tendency to wax. Wax precipitates from the crude when the temperature of the crude drops below the critical wax solubility temperature. The crude produced from the field under investigation has a maximum pour point temperature which is slightly lower than the reservoir temperature, which implies possible wax deposition during production.

Dynamically Coupled Reservoir and Wellbore Simulation Research in Two-Phase Flow Systems: A Critical Review

“…During start-up and shut-down, the well exhibited robust dynamics. Alberts et al [1] and Nennie et al [4], showed that the bottom hole pressure reached the reservoir pressure more slowly and was smaller than the initial reservoir pressure in the coupled model during the shut-in period. Forouzanfar et al [48] captured the clear wellbore storage effect by demonstrating an unstable constant pressure derivative value during the radial flow in the drawdown test.…”

“…In horizontal or deviated wells, the gas coning phenomenon reflected typical dynamic interactions between reservoir and wellbore. Belfroid et al [3]; Leemhuis et al [19]; and Nennie et al [4], noticed a lower bottom hole pressure and an earlier simulated gas breakthrough time in their dynamically coupled simulator, which performed slightly different simulation results from a standalone reservoir simulator.…”

“…Single reservoir simulation can hardly describe the gas breakthrough phenomenon due to a constant productivity index applied. A dynamic coupled wellbore-reservoir simulator was developed to simulate gas coning problems by Nennie et al and Leemhuis et al [3,4,19]. Figure 7 shows the BHP at different inflow control valves (ICVs) versus time during the gas breakthrough in a horizontal well with multizone completion by the coupled reservoir/wellbore simulator and simulator MoReS.…”

“…Consequently, the wellbore storage effect between the wellbore and reservoir must be considered during well testing. The researchers from Integrated System Approach Petroleum Production (ISAPP) simulated the dynamic well storage phenomenon to reveal the necessity of a coupled reservoir/wellbore simulator [1,4]. They stated that the coupled reservoir/wellbore model was a Matlab coupling between a single reservoir simulator MoRes and a single wellbore simulator OLGA.…”