Perm Journal of Petroleum and Mining Engineering (Dec 2016)
Mechanical system of layer protection and technology of its application to prevent clogging of bottomhole formation zone in performing geological and technical measures
Abstract
One of the important tasks of effective well operation in oil fields is to prevent clogging of bottomhole formation zone in the process of various geological and technical measures. As one of the most promising means to prevent reservoir productivity decreasing a technology using downhole shutoff valves has been proposed. Summary of the technology consists in application of a deep reservoir protection system, which is hermetically mounted in the well and dividing the productive formation area and pumping equipment placement. The analysis showed that the known shutoff valves configurations (systems with hydraulic, mechanical, electric drive) does not allow to carry out research on monitoring the development of operated object. Accordingly, none of the configurations has not been accepted for industrial use so far. The paper proposes a new mechanical reservoir protection system (including the bottomhole shutoff valve), providing a hermetic separation of productive reservoir and area of killing fluid injection when the differential pressure is up to 10 MPa. The basis of the shutoff valve construction is the principle of ball valve, in closed position the ball is pressed to valve seat by pressure, which creates a resistance to its opening. In order to achieve a high equipment`s operating time in design a special attention was paid to ensure device operation with the presence of well complications. To solve this problem a special sludge trap was included in the equipment and it was placed between the hollow plunger and the pump unit with a back pressure valve and a perforated pipe inside. Calculations of sludge trap filling were made according to the different number of stops and at various concentrations of mechanical impurities. As a result of calculations conclusions about the strength conditions fulfillment for geometric dimensions specified for pairs of steel-polyamide and steel-Zedex materials were made. Proposed device construction ensures a reliable isolation between under and above packer space, preventing ingress of killing fluid in the bottomhole formation zone. Universal equipment configuration extends its application area and the possibility of its use in combination with any pump unit depending on well conditions.
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