Oklahoma regulators on April 19 ordered a wastewater disposal well shut and told two operators to reduce injection volumes, the second such directive in less than two weeks after a series of earthquakes shook the state.

The Oklahoma Corporation Commission (OCC), which regulates the state’s oil and gas industry, directed privately held Choate Disposal Services to halt injections into a well in the Arbuckle Formation following a cluster of quakes around Hennessey, about 105 km (65 miles) northwest of Oklahoma City. The well was operating at about 9,500 barrels per day (bbl/d), according to the OCC.

That order comes less than two weeks after privately held M M Energy was told by regulators to reduce volumes on a large well in the Arbuckle after a series of quakes.

Oklahoma has suffered a sharp rise in temblors in recent years from the disposal of saltwater, a normal byproduct of oil and gas production. In 2015, the state experienced over 900 magnitude 3.0 or higher quakes, up from just 35 of the same intensity in 2012.

The OCC also told Sandridge Energy Inc. and SK Plymouth LLC to reduce injection into disposal wells in the Enid area that were within a 10-mile radius of the quakes.

Seven wells operating at 2,000 bbl/d must reduce their volumes by 25 percent, while another eight wells with volumes below 2,000 must remain within their last 60 day average, the OCC said in a press release.

The Enid area had already been operating under a 40% reduction since 2016.