Abstract
The Xining Basin in Qinghai Province, China, is rich in mid–low temperature geothermal resources, but the reinjection of geothermal water has not yet started. In this paper, the physical properties of rocks sampled from the newly drilled geothermal well DR2018 were analyzed, and a series of core flooding experiments was conducted to assess the formation blockage risk during water reinjection. The experimental results show that the geothermal reservoir has a low porosity of 1.64–18.68% and a low permeability of 0.04–7.23 md. The rocks are weakly consolidated, and the movable clay and sand particles account for 0.18–23.42 wt %, which results in a significant rate and salinity sensitivity. Even at low water flow velocity of 0.31–1.64 cm/min, the core permeability will drop by 35–53% after 25-144PV injection. An obvious fluctuation and decline in core permeability can also be observed as the injected water salinity decreases. The blockage risk induced by the invasion of low-content scaling and suspended particles in injected water can be covered up by the migration of movable particles in cores. The particle migration and blockage in the near-wellbore formation will be the main reason to cause the decline in the well’s geothermal reinjection capacity.
Highlights
As an important geothermal resource, deep porous geothermal water needs to be reinjected into reservoirs after utilization to avoid environmental pollution and formation deficit
Blockage Risk Caused by the Migration of Movable Particles
Cases 1–4 were used to assess the influence of water flow rate on the blockage risk during geothermal water reinjection using the cores 1130–11, 1130–12, 1130–13, and 1130–17 with a porosity of 6.53–14.19% and a permeability of 0.89–7.07 md
Summary
As an important geothermal resource, deep porous geothermal water needs to be reinjected into reservoirs after utilization to avoid environmental pollution and formation deficit. Geothermal water reinjection often faces a blockage risk in the nearwellbore formation. In some high-risk cases, it may lead to a dramatic decline in the reinjection capacity and even make the wells shut down [1]. China is rich in mid–low temperature geothermal resources, but the reinjection project has not yet started, which greatly limits the efficient development of geothermal energy in the Xining Basin. It is of great significance to carry out research on the blockage risk in the formation during geothermal water reinjection. There have been many studies on geothermal reinjection blockage around the world. Ochi et al [2] found that the hydrodynamic effect of particle migration caused by fluid injection into sandstone reservoirs can reduce the permeability by more than 50%
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
