Operational Energy Savings through the use of Continuous Sucker Rods with Progressing-Cavity Pumps

Abstract

Abstract This work analyzes the difference in energy requirements between using continuous sucker rods and using conventional jointed sucker rods in Oilwell Progressing-Cavity Pumping (PCP) systems, with an emphasis on how each rod type is affected by well depth and fluid content. PCP is a rotational pumping application; these pumps transfer fluids through internal cavities by rotating a rotor inside of a stator. Calculations for this study are performed with a computer spreadsheet to illustrate potential energy savings achieved with continuous rod applications. This work expands on previous research addressing continuous sucker rods by observing how changing viscosity (with increasing well depth) can affect pump operation. The focus is on production in the San Joaquin Valley, which typically has high water-to-oil ratios; the properties of brine water and 14° API crude oil are used in the calculations. Oilfield operators planning to install PCP systems can use data acquired from this work to estimate the influence of several factors on pump operational energy costs. Results can be iterated from this study to estimate different operating situations depending on the particular well conditions. This study is also an attempt to understand anecdotal evidence found in existing wells with PCP and continuous sucker rods already installed Using a continuous rod results in operational energy savings over conventional rod strings, the magnitude of which depends on well depth and fluid content. The author concluded that the increased energy savings were a result of omitting couplings and guides from the rod string. Couplings and guides decrease the annulus area for the working fluid to flow through, which increases pump pressure requirements. Greater savings are observed in deeper wells because the rod string is longer, which requires more couplings and guides on a conventional rod string. Predicting the operational energy cost savings attained by using a continuous rod can help determine whether the capital cost of installing continuous rods will be recouped in a profitable timeframe. Calculated energy savings may also be used towards applying for energy saving incentives through California utilities customer energy efficiency programs, which can help offset the investment in energy-efficient building and design and ultimately lead to a higher return on investment.