Ever since the first installation of steel sucker rods in production tubing, the Petroleum Industry has been aware of rod string and tubing wear. The associated rod string and tubing wear with this artificial lift system continues to have an impact on the ability to economically produce oil and gas.
The downstroke phenomenon of sucker rod string compression, buckling, sucker rod/tubing contact and associated sucker rod/tubing wear is becoming more clearly defined (see References 1,2, and 3) throughout the petroleum industry.
This paper will provide the Petroleum Industry with a more accurate understanding of sucker rod and tubing wear resulting from sucker rod side loading initiated by downstroke sucker rod buckling. This paper will present a description of test equipment and test parameters resulting in the following:
Calculated cycles to 100% tubing wall loss vs. side loading.
Calculated cycles to 100% sucker rod diameter loss vs. side loading.
Calculated cycles to 100% sinkerbar diameter loss vs. side loading.
A better understanding of sucker rod and tubing wear will provide the Industry with better sucker rod string design guidelines. Use of these guidelines can reduce costly sucker rod and tubing wear and failures that impact the ability of the Petroleum Industry to economically produce oil and gas.
The test equipment designed for this experiment simulated vertical sucker rod and tubing wear in a horizontal configuration. The tubing reciprocated in a horizontal plane, while the rods and sinkerbars were loaded during the full stroke with various static loads. These static loads were selected to simulate side loads acting on the interior wall of production tubing during lift operations. This test equipment was designed to handle four (4) separate test configurations of rods and sinkerbars in tubing. All four (4) test configurations were submerged in two (2) separate containment vessels to simulate rod string and tubing wear in fluid media environments.
The test parameters for this experiment were selected to simulate as close as possible rod string and tubing wear experienced by rod strings operating in compression in tubing. The selected test parameters are listed as follows: