Wellbore Heating Study

A wellbore heating study was commissioned to iProdTech by a global E& P company for an onshore field development in East Africa. The reservoir fluid has a high wax content with relatively high wax appearance and pour point temperatures which are expected to cause flow assurance issues. Electric downhole heating and hot water circulation was utilised during extended well tests in appraisal wells to maintain flow at surface and prevent the oil solidifying when the wells were shut in. Current plans envisage multi-well pads to be used to drill development wells. In order to progress into the Full Field Development, iProdTech services were utilised to help understand the effect of various heat retention and/or heat addition methods and whether they are required to help mitigate the flow assurance issues.

The main objectives of the study were to:

  • Develop calibrated thermal models of the two EWT production wells using the available fibre optic distributed temperature sensed (DTS) data available from the production phases of the EWT.

  • Conduct sensitivity studies using the calibrated well thermal models to evaluate the effect of the following on flow assurance:

    • Specialist cements

    • Insulating packer fluids

    • Hot water circulation

    • Downhole electric heating

  • Additionally, an initial assessment of the level by which the pour point temperature may need to be lowered with any of the above techniques was required.

  • Analyse the trial shut-in/cool down periods from the EWT production phase to develop initial estimates of trouble-free production re-start times as a function of shut-in duration.

  • Assess the impact of multi-well pads on the development of a ‘heat sink’ and the effect on shut-in/cool down behaviour.

Accounting for the thermal interaction between wells, particularly in the shallow overburden where the wells are closely spaced, was identified as an important consideration for this work. Petroleum Experts’ REVEAL™ software was therefore selected for the study as it allows the modelling of various heat retention / addition techniques along with the thermal interaction between multiple wellbores.

The extensive data set available including EWT flow and pressure data, permanent DTS installation, downhole electrical heating and extended cooldown times has provided a unique opportunity to model and analyse flow assurance challenges in the field. This is the first time that iProdTech are aware of any detailed modelling being undertaken of the thermal interaction between wells and detailed calibration of DTS / heater strings during an EWT.