Publications

Wells producing from sucker rod pumps are rarely tested for damage due to the expense and inconvenience of pulling the rods. We present a simple and elegant method to estimate the productivity index, PI, and the damage, or skin, of a rod pumping well utilizing only the knowledge of pump runtime vs. downtime. The technique does not require well intervention.The method is an inverse solution as is found in conventional well test interpretation. A theoretical or model pump runtime is computed assuming the two unknowns (PI and skin). The model is then compared with the actual runtime data. The unknowns are updated and the process is continued, either manually or automatically, until the model matches the measured data. The average reservoir pressure is assumed to be known from an independent source.The method lends itself to real-time production management as the required data may be continuously and automatically transmitted to a central location upon which, following the algorithms developed here, the behavior of the well/reservoir system may be monitored and the flow rates optimized. Furthermore, in conjunction with dynamometer information, declines in production may be immediately diagnosed as either a mechanical or reservoir problem. The value of the technique is illustrated using field data.