Downhole Heating Device to Remediate Near-wellbore Formation Damage Related to Clay Swelling And Fluid Blocking (1998)

Abstract It is a well-known fact in the petroleum industry that thermal treatment (wellbore heating) could result in significant benefit to the producing wells by remedying fluid related problems. Recently, it bar been shown in the literature that thermal stimulation also improves fluid flow characteristics of the near-wellbore porous region. To conduct wellbore and near-wellbore thermal treatments, a simple retrievable electrical down hole heating device has been designed constructed, and tested. The down hole heating system contains a separate heating chamber, wiring chamber, and cooling chamber. The cooling chamber is inserted between the wiring chamber and the heating chamber to prevent heat propagation from heating chamber to the wiring chamber. The heating is carried out at the surface to test the heater's capability. An inert gas at the ambient temperature condition is injected through the tubing and heated to the desirable temperature as it passes through the heater. Results indicate that by controlling the power input and the carrier gas flow various desirable temperatures can be achieved. Introduction Conventional hydrocarbon producing wells encounter various problems during their production life. These problems are either related to fluid characteristics or related to formation rock characteristics. Fluid related problems are primarily related to deposition of wax and asphaltene materials and creation of water-in-oil emulsion and these problems can occur in the wellbore tubular and accessories (i.e. surface equipment, wellbore pumps, pumping rods etc.). In addition, these problems could also occur in the near wellbore regions of the rock The reservoir rock related problems are primarily caused by fluid invasion resulting in clay swelling and fines migration. Acid treatments are very popular in remedying the problems related to formation rock characteristics, especially, for carbonate reservoirs. However, acid treatments have had mixed success in remedying formation rock-related problems in sand stone reservoirs. Thermal treatment (wellbore heating) could result in significant benefits to the producing wells by remedying fluid related problems. Recently, it has been shown in the literature1,2 that thermal stimulation also improves fluid flow characteristics of the near-wellbore porous region. The foremost application for heating a formation has been to reduce the viscosity of the oil, specifically heavy oil3–13. A second important application for heat treatment has been the prevention or removal of waxes or asphaltenes build-up2,4,6,14,15,16 the wellbore and near-wellbore region. Other benefits resulting from thermal treatments include clay dehydration,3 thermal fracturing at high temperature, prevention of thermal fracturing in water zones at low temperatures11 and sand consolidation17 in unconsolidated formation. In the case of down hole electrical heating some of the current may be diverted to prevent the corrosion of tubing, casing, pump rods and other down hole components and to prevent build-up of corrosion products. Most down hole heating devices have been designed to apply to combustion or down hole steam generation purposes. A down hole electric heater is designed to use to ignite the in-situ fuel.3 The heater is removed and air is supplied to maintain a combustion front. An ohmic4 heating system has also been applied for an oil, which had a viscosity of 160 mPa.s.