Mechanism of Salt Precipitation Blockage in Low-Producing Gas Wells and the Method of Acidification Blockage Removal.

ABSTRACT

In the Changqing area, over 23.6% of gas wells produce less than 0.1 × 104 m3/d of gas daily, posing a challenge to gas field sustainability. Laboratory analysis of scale samples from three wells and formation water analysis via inductively coupled plasma revealed soluble salt as the primary well blockage, with sodium chloride and calcium chloride comprising 48.0-81.2% of total content. The G3# well blockage contains a small amount of quartz from acid-insoluble components of carbonate acidification. Formation water from all wells exhibited high salinity (up to 153 g/L) with a calcium chloride water type. Scanning electron microscopy and EDS confirmed halite and quartz features in blockage samples. Theoretical calculations show salt crystallization when tubing pressure falls below 10 MPa and daily water production is <1.0 tons/day. Lower production leads to lower tubing pressure and higher salt precipitation at the bottom of the well. For G1# and G2# blockages, HCl dissolves >90%, and water >85%, making them suitable removal agents. For 3# blockage, mud acid with >80% dissolution is recommended. Chemical methods effectively clean the wellbore and formation. Optimized blockage removal measures increase tubing pressure and daily production by 2.18 and 4.05 times, respectively. This study offers insights into addressing well blockage challenges in low-producing gas wells.