The First Experimental Hydraulic Energy-Storing Workover Rig XXJ 300/600

Abstract

Abstract The hydraulic energy-storing workover rig is a new type of rig invented by the authors of this paper. The first experimental rig has passed through field test (see Fig. 1). This rig differs from other types of workover rigs not only in appearance but also in working principle. There is an energy-storing system, so some energy issued from motors or from running down pipestring can be stored and used later when needed. This new invention has obtained a lot of advantages such as energy saving, safety, less noisy, possibility of using hydraulic tubing tongs without another hydraulic system, etc. Background Nowadays, oil well workover rigs (or service rigs) are basically similar. Most of them are composed of engine, power transmission system, drawwork, derrick, crawn block, travelling block, etc. During operations, the tubings, which weigh tens of tons, are putted down in the wells and lifted up from the wells repeatedly, consuming a lot of fuel. When a single or a stand of pipe are picked up from a well, the pure lift time is only about one third to one fourth of total time necessary for complete a circle of lifting a single or a stand. The rest of time is for auxiliary operations. But the equipped engine power should be large enough to meet the requirement in pure lift time. Powerful engine consumes more fuel even at idle or nearly idle working conditions. Furthermore, when the pipestring is lowering down, the engine cannot be stopped either, although the going down pipestring issues a large quantity of potential energy, which must be wasted uselessly by braking. How to raise the efficiency of rig, how to recover (even if only partly) the potential energy of pipestring? To solve these problems is the purpose and result of this invention. DESCRIPTION The concept of energy-storing rig was completed in 1991. Later a feasibility study was taken place and the first experimental energy storing workover rig named XXJ 300/600 (see Fig. 2, 3) was designed and manufactured. Factory test and field trial were fulfilled in 1994. It is not easy to store motor power, especially to store and recover potential energy of pipestring, although partly, because of the energy which should be stored is intermittent and its volume is changed gradually at all time. For this reason, the rig has had a unique design. P. 223