Study on evaluation method of drilling fluid-salt formation interaction based on radial flow equivalence

Abstract

During the processes of drilling fluid circulation and cementing operation, the working fluid in the wellbore annulus mainly exhibits axial flow. Traditional large-scale axial flow simulation devices, such as horizontal well drilling fluid sand-carrying devices, can relatively truly reproduce the flow state of working fluid. However, they have problems including large volume, high cost, and inconvenience in operation and maintenance, which result in low utilization rate in conventional experiments. To date, no dedicated device has been developed for the simulation of axial flow by means of radial flow. This study proposes a new method that uses radial flow to simulate axial flow, aiming to evaluate the performance changes of oil and gas field working fluid when it flows through salt formations, as well as the effects of erosion and contamination on salt formations caused by the working fluid. It conducts research on the interaction method with working fluid as the subject and salt formation as the object, deduces the equivalent semi-theoretical formula between radial flow and axial flow under the conditions of shear rate and contact area, and develops a set of simulation experimental devices. The innovation of this study does not lie in the radial flow equivalence principle itself, but in its specific application to the solid-liquid coupling of drilling fluid-salt formation and the full-chain simulation of erosion-dissolution-contamination in salt formations. Taking laboratory experiments as an example, after 120 min of erosion on the salt formation by two drilling fluid systems (DSP and JHJS) optimized through this evaluation method, the variation range of rheological properties and fluid loss performance is 5%–10%, the dissolution depth of the salt formation is tiny, and the surface morphology remains unchanged. This method can provide an operable experimental means for the evaluation of drilling fluid salt resistance and the optimization of drilling formulas for salt formations. It also has guiding significance in practical construction, as it can realize cycle optimization in both deep wells and medium-shallow wells, and provide reliable technical support for the design and on-site application of drilling fluid systems under complex well conditions.