The Autonomous RCP Valve - New Technology for Inflow Control In Horizontal Wells

Abstract

Horizontal wells with one or more branches have been used to maximize reservoir contact by Statoil and other oil companies for more than a decade. Frictional pressure drop and variation in permeability and mobility will naturally lead to non-uniform inflow profile along a well. Eventually, this will result in gas and/or water breakthrough, which may reduce the well performance and recovery significantly. The breakthrough typically occurs in the heal region of the well and in regions with high reservoir permeability. Inflow Control devices (ICDs) are flow resistance elements installed along the producing zone of a well to counteract the non-uniform inflow, hence improving the well performance. The technology is regarded as standard technology by the industry and classified as passive inflow control, since the geometry of the devices is fixed or preset prior to installation. Passive inflow control is applied to delay the unwanted gas/water breakthrough. However, once occurred, conventional inflow control will not reduce or stop the breakthrough. Statoil's new autonomous inflow control device (AICD) is an active flow resistance element distributed along the well, similar to conventional passive ICDs. Statoil's AICD will, in addition to delay the breakthrough, reduce the proportions of the breakthrough. The AICD will impose a relatively strong choking for low-viscous fluids and only minor choking for viscous oil. This is due to autonomous changes in the flow area internally in the AICD. With this technology the well performance and production can be higher after a breakthrough compared to conventional inflow control. Statoil's AICD technology is piloted in two wells at two different fields in the North Sea. Each well is completed with 1-4 AICDs per screen joint, typically 200-400 per well. The AICD operates without need for human interventions and electric or hydraulic power. Well tests have shown that Statoil's AICD technology reduces the inflow of gas into the well from a reservoir containing light oil. Due to the restriction of the gas inflow, the drawdown can be kept high after breakthrough to allow significant oil production from the remaining oil zones in the well. Likewise, in a pilot well in a reservoir containing heavy oil, well tests have shown that Statoil's AICD technology reduces the inflow of gas into the well and preliminary evaluations indicate that even water inflow is reduced. Thus the drawdown can be kept high allowing high production from the remaining oil zones.

Computational Study of Heavy Oil Production with Inflow Control Devices

“…AICDs can therefore be classified as 'smart' devices that are capable of changing their response depending on the properties of the inflowing fluid. Different types of AICDs are developed and the different principles are described in literature (Mathiesen et al, 2011;Halvorsen et al, 2012;Least et al, 2012;Aakre et al, 2013).…”

“…The study is related to California heavy oil reservoirs. The work focuses only on the AICD developed by Statoil ( (Mathiesen et al, 2011;Halvorsen et al, 2012), and a function describing the functionality of this type of AICD is used in the simulations. This is assumed to be the most accurate interface tracking scheme, and is recommended for most transient VOF calculations.…”

“…The AICDs are modeled as porous regions and a power law model is describing the functionality of the valves according to Equation 2. The pressure-flow rate characteristics of the AICD is defined as below (Mathiesen et al, 2011):…”

“…This implies that the pressure drop across AICD depends on a combination of the fluid properties and design variables. Constants used for the AICD valve function in this study are tuned based on data presented by Statoil (Mathiesen, 2011;Halvorsen, 2012) …”

Near well simulations of heavy oil production with ICD completion

“…The economical situation all around the world and the high availability of heavy oil recourses are the two main reasons which make these resources more valuable than ever before [1]. Horizontal drilling have been developed and utilized successfully during the past decades which enables more efficient production from long thin oil deposits by enhancing reservoir contact and thereby optimizing well performance [2][3][4][5]. However, there are still challenges regarding early water or gas breakthrough due to the frictional pressure drop along the well, reservoir heterogeneity and annular flow which impacts the production.…”