Downhole seal for low profile oil well pumping installations

摘要

Set out herein is a seal arrangement for sealing an oil well rod string below ground surface. More specifically a polished cylinder is inserted into the casing of an oil well and is supported at the well head by a flange radially extending from the upper end thereof. Received in the cylinder is a piston assembly connected at the upper surface to a flexible string or chain articulated by a pump and supporting at the lower surface a polished rod sealably extending through a lower seal fitting received in the bottom end of the polished cylinder. The cavity formed between the piston and the polished cylinder is aspirated into the well casing through a one-way check valve on the upward stroke of the piston and any oil residue that may pass through the lower sealing assembly is forced back into the well casing by another check valve opened during the downward piston stroke. Both the piston and the seal assembly may include sealing rings to improve edge contact which thus render the downhole seal less vulnerable to hot gases and abrasive impurities commonly found in the course of secondary recovery.