CO2 Quasi-Dry Fracturing Technology and Field Application in the Lulehe Formation of the Qaidam Basin

Sensitive reservoirs with high clay content commonly suffer from severe water/salt sensitivity and water-lock damage during conventional water-based hydraulic fracturing, which reduces fracture conductivity and post-stimulation performance. To address this issue, we propose a CO2 quasi-dry fracturing approach that combines the low-damage feature of CO2 dry fracturing with the proppant-carrying capacity of a water-based system under atmospheric sand mixing conditions. Taking Well S in the Lulehe Formation (Qaidam Basin) as a case study, we conducted reservoir sensitivity evaluation, laboratory fluid/rock interaction tests, and a field trial with microseismic monitoring. The reservoir is dominated by water and salt sensitivity, indicating high risk of damage when using conventional fluids. Laboratory results show that the CO2 quasi-dry system improves swelling inhibition and enhances core structural stability compared with fresh water. Field implementation was operationally stable and generated an effective stimulated reservoir volume on the order of 105 m3; post-fracturing oil production increased relative to nearby offset wells with a high flowback ratio. The results demonstrate that CO2 quasi-dry fracturing provides an effective low-damage stimulation option for strongly sensitive reservoirs and can be transferred to similar formations.