Large-Scale Field Validation and Practical Application of a Multi-Well Thermal Interaction Model for Temperature Simulation

Abstract

The wellbore and formation temperature environment around a system of multiple wells in close proximity is complex. Temperature simulation and prediction for a single isolated well is simplified by axisymmetric assumptions. Realistic multi-well environments do not have obvious symmetry and are interactive given different operating states including possibly a mix of producer versus injector wells. A simulation model of thermal interaction between closely spaced wells has been developed in a collaborative project. A large-scale validation of the model is presented here. An important field application is presented for a subsea well template where movement tolerances must be tightly controlled. Large-scale validation was conducted for an offshore platform development where more than 30 wells were drilled and brought onto production over a period of 4-5 years. As each well was drilled and completed, temperature logs where recorded which thereby gave a digital signature of the complex thermal environment below mudline as it evolved over time. The simulation model temperature for each well was corroborated against well temperature logs. A simultaneous boundary-condition of flowing wellhead temperatures and pressures for each well was compared against the model predictions. Also, a detailed predictive case study is presented for a 6 well subsea template. Model temperatures were used to assess the impact of cement height on wellhead movement within the template structure which featured lockdowns and tight tolerances on allowable movement within the housing profile. Predicted temperatures from the multi-well model agree closely with logs and correlate closely with characteristic temperature excursions from geothermal below the mudline down to the well path kick-off zone. Since the logs occur over time and account for a changing well population, the model is shown to accurately capture the time evolution of the complex temperature environment. The model explains unusual temperature log signatures as the result of sidetracks and the radial extent of heat affected zones from the parent wellbore. The subsea case study highlights the importance of predicting the complex multi-well temperature environment by demonstrating its impact on the wellhead movement given the uncertainty of cement tops for deeper shoes of combined conductor/surface casings. This learning informs subsea template design and selection with port options for cement grout and top-up jobs. Although the multi-well temperature model has been presented previously along with some field data validation, the large-scale study presented provides further and significant model validation. Extensive data over time and corroboration with unusual temperature log phenomena demonstrate model accuracy. The utilization of the model in the design and specification of a subsea template development provides a real-world example and demonstrates practical application as well as its usefulness.