Objective and scope
In different production scenarios, the partial shutting of the choke valve can be a suitable alternative to sustain the oil production rate in case of high gas-oil ratio (GOR) or excessive gas production. However, it has been observed that this procedure can lead both produced liquids: oil and water, to out-of-spec conditions, thus causing production losses and hurdles to water management and disposal, especially in offshore production installations where the capital expenditure (CAPEX) and the operational costs (OPEX) are traditionally high.
To shed light on this problem a comprehensive evaluation of the produced fluids properties was carried out. Also, both pressure and temperature profiles along the production process were monitored. The big change noticed by the operation team was the sharp temperature drop (< 20°C) of the produced fluids arriving at the topside facilities when the wells were choked-down This thermodynamic phenomenon is provoked by gas expansion, the so-called Joule-Thomson (cooling) effect. In this way, a series of lab tests were performed to mimic the operational field conditions. After analyzing the lab results, an alternative solution was proposed to avoid the drawback of producing out-of-spec fluids, whenever necessary to partially close the choke valve during oil and gas production. This is especially true when waxy crude oils are produced at low temperatures, thence increasing the probability of formation of both Pickering-type- and/or viscous- emulsions.
