Fluid Cool Down vs. Heat Back - An Analysis of Bottomhole Gauge Temperature Responses to Optimize Stimulation Fluid Clean Up and Thereof Testing, Offshore Black Sea

In an effort of maximizing the production from low permeability reservoirs in mature fields, operators often strive to implement innovative technologies and engineering approaches that can help achieve that goal. This paper presents an analysis of the temperature responses from bottom hole gauges of several horizontal wells that have been stimulated offshore Black Sea. The analysis covers the fluid cool down and heat back profile during stimulation and production. Ultimately, the analysis’ goal being to better understand the rheological properties of the stimulation fluid and enhance well clean-up by avoiding miss-allocation of temperature ranges during fluid testing for when the well is brought on production. Based on available data from bottom hole gauges implemented in the horizontal wells stimulated in the Black Sea, an analysis of the temperature gauge responses has been performed. The analysis includes a workflow of temperature change validation per well, considering fluid pumped per port in stimulation phase and fluids produced per port in production phases. The fluid production allocation per port was done utilizing chemical tracer technology results. Stimulation treatments in the same reservoir offshore Black Sea, Romania have been analyzed in terms of bottom hole gauge readings of temperature during the stimulation fluid pumping and during the early production period of each well. A workflow was implemented on each well to correlate fluid per stimulation stage pumped to temperature changes during the treatments. Similar approach was used to correlate the temperature heat back profile during the shut in of wells in the initial 48 hours for proppant curing to the production phase clean-up of the wells. The observed cool down during pumping was of no surprise, but the heat back indicated a slower process of warm back that affects the stimulation fluid testing approach and the understanding of possible near wellbore pressure differentials caused by misallocation of temperature range testing of pre job rheology tests. A combination of temperature data with diagnostic tools and the pertaining analysis will provide a better description of wells’ performance. In conclusion, misinterpretation of modelled cool down and reservoir heat back can lead to erroneous understanding of fluid clean up, ultimately affecting reservoir fluid inflow. Understanding the areal temperature response helped optimize fluid testing approach and plan for better clean up. The approach and the sensitivity analysis results are beneficial in understanding the temperature behavior during treatment pumping and production of stimulated wells. This process can enhance an engineer's approach in scrutinizing stimulation fluid testing for improved post stimulation clean up.