Advancements of Fracturing Technique Implementation to Jurassic Formations of Uvat Region

摘要

To provide designed oil production and to minimize non-productive time new approaches in hydraulic fracturing have been tried and introduced for several years in Uvat project. During this optimization process, several new technologies were pilot tested including fiber-laden fluid, rod-shaped proppant and channel fracturing technique. The main goal was to improve fracturing fluid reliability and to decrease the risk of premature screen-outs in combination with more aggressive fracturing design to maximize oil production. Uvat project oil field is located in Western Siberia. Jurassic formation is the main oil producer from the field, presented by significant net height (up to 45 m), relatively high permeability which varies in wide range from 2 md to more than 50 mD. The formation temperature is 80-90°C. The requirements to fracture geometry is gradually increase in these conditions. The greater fracture width must be accompanied with sufficient effective fracture half-length. This goal cannot be achieved with standard hydraulic fracturing techniques because of limitations in proppant pack conductivity. Besides, the more aggressive design is associated with the higher risk of premature job screen-out that consequently results in non-productive time. Paper describes the results of pilot projects for the following new technologies introduction: fibers that allow better proppant distribution in the fracture and decrease polymer concentration without sacrificing proppant transportation ability of the fluid (the new generation of fibers was implemented which is for low temperature formation); rod-shaped proppant to prevent particles flowback and to increase fracture conductivity; channel fracturing technology that allows to decrease treatment costs and risk of premature screen-out while keeping or even increasing the flow capacity of the fracture. In channel fracturing application a proppant is added in short pulses alternated with clean fluid pulses. This becomes even more vital in remote locations as the same stimulation result can be achieved with less proppant amount replaced by clean fluid pulses that leads to decrease in spending on logistics and time optimization for fracturing job. The manuscript describes the candidate selection methods for re-fracturing jobs and states the main success criteria (such as presence of formation energy and current skin calculation). The authors represent comparative analysis of horizontal wells and multistage fracturing effectiveness in low productive regions resulted in high incremental oil rate when compared to vertical wells with a single fracture.