Controlling Post-Completion Flow in Steam-Assisted Gravity Drainage Wells

Abstract

Technology Update The rapid growth of unconventional oil and gas production in the past decade is largely a result of advances in horizontal drilling techniques that allow longer laterals to reach deeper into the formation. While this well design is attractive because of the contact it affords between the wellbore and the formation, it does not come without production challenges. For example, rather than achieving consistent or near-uniform production across the entire lateral, certain sections might be favored for production over others. This undesirable outcome arises from several factors, including the influence of frictional pressure drop in the completion string, reservoir heterogeneities, changes to fluid composition and mobility, breakthrough of undesired fluids (i.e., water or steam), and variations in reservoir pressure along the wellbore. This results in an unbalanced inflow profile, diminished production, and subeconomic well performance. Historically, operators were left with limited options to address these issues, short of the costly decisions to recomplete the well or drill a new one. Over the past 15 years, operators have increasingly installed inflow/injection control devices (ICDs) during well construction to avoid the problems. These devices are placed strategically along the lateral to balance the production/injection profiles across the entire length and to compensate for variations in permeability. Recovery and injection performance have improved as a result. A Retrofit Device However, until recently, ICDs could only be effective when installed as part of the initial completion. To address uneven production in existing wells without flow control systems, Baker Hughes has developed the Equalizer retrofit (RF) device, the industry’s first ICD designed to be installed post-completion. The RF ICD is able to equalize production flow across the entire lateral and restore a well to its desired performance level. While the retrofit system is applicable to most production scenarios, it has found the most applications to date in steam-assisted gravity drainage (SAGD) wells (Fig. 1). Common problems in SAGD wells include inadequate fluid production control in the completion, which leads to uneven steam conformance, lower sweep and thermal efficiencies along some sections of the lateral, adverse heel-to-toe effects, and the risk of live steam entering the producing well. The RF ICD system allows operators to install one or more flow control devices inside the existing completion (whether executed with a slotted liner or a screen) by means of tubing to equalize the inflow of hydrocarbons. This gives operators the flexibility to install inflow/ injection control equipment after the completion is in place, or replace existing systems to reduce costs and maximize ultimate recovery from existing wells. These systems are typically installed with high-temperature packers rated up to 300°C (572°F), which serve to compartmentalize flow in certain areas of the well. These packers help to channel production through the ICDs, block off damaged liner zones, and improve recovery along the length of the wellbore. The RF ICD incorporates many of the design elements of the service provider’s previous generation of flow control technology, including a tortuous flow path geometry. The flow path gives selective resistance to gas, steam, and water breakthrough. Should one or more of these undesirable fluids enter the ICD, the pressure drop across the device increases, causing the unwanted fluid to be choked back to avoid breakthroughs in the lateral. For desirable fluids (i.e., oil), the pressure drop across the device decreases, thus allowing selective production.