NodalB : A Unique Program for Optimum Production of Sucker Rod Pumping Oil Wells

NodalBc: A Unique Program for Optimum Production of Sucker Rod Pumping Oil Wells Abstract Sucker rod pumping is the oldest artificial lift method used in production of oil wells. This method is usually designed and analyzed with the assistance of programs based on simplified models, such as the API RP 11L, or with a wave equation simulator. In many cases, however, a technique that permits consideration of the inflow and outflow performance of the well is a more efficient way to design and analyze an oil well. This technique, referred to as Total Analysis or System Analysis (SA), has been successfully applied to flowing and artificially lifted wells. This paper presents a computer program developed by Intevep S. A., called NodalB, created to perform the SA of sucker rod pumping wells. NodalB 's unique characteristics make it a competitive program in today's market of design and optimization software. This program allows consideration of the inflow performance of the reservoir depending on the drilling scheme, either vertical or horizontal, and determination of the sensitivity of the rod pumping system to its most relevant parameters, such as: pumping speed and stroke, pump diameter, gas oil ratio, gas separation efficiency, tubing diameter, pump depth, rod string design, oil viscosity, injected diluent (diesel, kerosene, etc.) ratio, water cut, reservoir pressure, productivity index, and different production schemes (i.e. production through the tubing or through the casing-tubing annulus). These features show the power of this program as a predictive tool. NodalB is specially applicable to design, optimization and troubleshooting of heavy and viscous oil wells, taking into account the viscosity effects in the rod pumping system. Introduction The current total oil production of Venezuela is approximately three (3) millions of barrels per day. One million of it is produced from almost 7000 sucker rod pumping wells, and consists, in its majority, of heavy oil and bitumen, which typical downhole viscosity ranges from 500 cp up to 7000 cp. The corresponding API gravity ranges between 8 and 12. Due to the high viscosity of the oil, cyclic steam injection has become a typical production scheme for those wells in which static reservoir pressure is below 1000 psi (up to 2500 ft of well depth). Also, other alternative production schemes have been developed to reduce 1) the drag forces between the rod string and the fluid and 2) the pressure drops in the tubing string and flowline. Such schemes involve the injection of a low viscosity fluid (diesel, kerosene) in a continuos basis into the wellbore and flowline. Furthermore, the oil being produced usually flows through the tubing-casing annulus instead of the tubing. Recently, a new completion scheme, called the Downhole Stuffing Box Production Scheme, has been successfully tested in the field, revealing several advantages over the other heavy oil production schemes currently applied in Venezuela. P. 33