James N. McCoy

Acoustic Determination of Producing Bottomhole Pressure

This paper discusses the acoustic determination of producing bottomhole pressure (BHP). Two different techniques are presented for wells that have liquid above the formation and gas flowing upward through the gaseous liquid column. One technique involves the acoustic measurement of the liquid level and the casing-pressure buildup rate when the casinghead valve is closed. When these data are used along with an empirically derived correlation given here, the gradient of the gaseous liquid column in the annulus can be obtained. This technique offers a reasonably accurate procedure for determining the producing BHP of a well by acoustic means. The second method involves two acoustic measurements. A backpressure valve is used in the casing head to depress and to stabilize the liquid level at two positions while the well is produced at a constant rate. The gradient of the gaseous liquid column is then calculated and extrapolated to the formation depth. This paper discusses results from the field testing of numerous wells where the actual gradients of gaseous liquid columns were measured in a variety of casing/tubing sizes, oil gravities, gas flow rates, and pressures.

Best Method to Balance Torque Loadings on a Pumping Unit Gearbox

In general there are three methods available to the operator to determine the net torque loading on a pumping units gearbox. Two dynamic methods determine the instantaneous torque throughout the pumping cycle. Method 1 combines the measured surface dynamometer card and calculated torque factors with measured or calculated counterbalance moments from the crank and weights. Method 2 uses measured motor power with motor and drive efficiencies and the pumping unit speed to calculate gearbox torque. The third method combines the counter-balance effect (CBE) with measured dynamometer loads and the torque factors to compute the net torque on the gearbox. The CBE test is a direct method of determining net gearbox torque at a specific crank position to estimate the maximum counterbalance moment. This static test is where the cranks and counter-weights are held level until no upward or downward movement is noticed when the break is released. Field case studies applying all three methods to determining gearbox torque are presented in this paper. The pros and cons of using each method are discussed.

Beam Pump Balancing Based On Motor Power Utilization

Recent application of a portable computer-based instantaneous power meter which is easily connected to a beam pump`s switch box, has made it possible to study in detail the effect of counterbalancing on electrical consumption and operating cost. This paper describes the measurement system as well as its application to determine the power usage per pump stroke and the gear reducer torque. A simple algorithm is presented for the determination of the counterweight adjustment required to modify the peak torque or the power use. The results of accurately monitored field tests for a variety of beam pumps and well depths are presented in detail. The measurements indicate that unit balancing based on instantaneous power, yields results similar to those obtained from torque derived from dynamometer measurements using a horseshoe type load transducer. The ease of installation of the power probes compared to installation of the dynamometer makes this the preferred method for most beam pumping systems powered by electrical motors.

Pump Intake Pressure Determined From Fluid Levels, Dynamometers, and Valve-Test Measurements

Three pump-intake-pressure (PIP) calculation methods available for wells artificially lifted with sucker rods are discussed in detail in this paper. The values of PIP obtained from acoustic fluid-level measurements in wells with moderate pump submergence can yield PIP estimates that agree with those of pump fluid-load analysis. If PIPs determined using these methods do not agree, then the operator must review the data quality and may reduce the deviation by adjusting certain parameters affecting the calculations. Field data for a significant group of wells are used to compare the PIP results of the three methods. The results show that the PIP computed using the maximum and minimum pump dynamometer loads usually calculates a PIP that is too low, while the PIPs computed using the valve test loads are usually too high. Recommendations are presented for quality control of the computed values.

Tubing Anchors can Reduce Production Rates and Pump Fillage

Modern completion techniques have greatly increased the production rate capability of wells. Many wells have the potential to produce more liquid and gas, but the use of tubing anchors in certain wellbore locations chokes the gas flow up the casing and results in increased back pressure against the formation that restricts production from the well. A gaseous liquid column can form above the tubing anchor and cause high pressure in the gas below the tubing anchor that restricts the liquid and gas flow from the reservoir. Often times, low pump fillage and low production rates are blamed on a poor gas separator when actually the separator is operating efficiently and is separating the liquid from the gas. In the condition described, all of the liquid in the wellbore below the tubing anchor falls to the pump and is being removed by the pump. The problem is that high pressure in the gas column below the tubing anchor is restricting production from the well. Additional production is available if the high pressure that is restricting production from the formation is removed. The accumulation of a gaseous liquid column above the tubing anchor indicates that liquid exists above the tubing anchor when only free gas exists from the tubing anchor down to the pump. Limited liquid production falls down the casing wall while the casing annulus is almost completely filled with gas if the pump is set below the formation. Field testing using automated fluid level measurement equipment to perform fluid depression tests verifies that a gaseous liquid column exists above the tubing anchor and a gas column exists below the tubing anchor in some wells. This field data was acquired on several wells and is shown to verify the above analysis of the well’s performance. This fluid distribution condition is not general known. Locating the tubing anchor below the pump prevents this condition and will improve production in these wells.

Total Well Management - A Methodology for Minimizing Production Cost of Beam Pumped Wells

A procedure is described that allows an operator to identify those beam pumped wells which are operating at reduced efficiency. The logical sequence of steps to be followed in acquiring performance data such as power, dynamometer, fluid level, etc. and the criteria to be used in determining the causes of inefficiency are presented with the objective of reducing the time and effort required to perform the analysis.

Low cost wellsite determination of bottomhole pressure from acoustic surveys in high pressure wells

The risk and cost involved in undertaking bottom-hole pressure surveys by wireline in high-pressure gas wells, especially those which produce sour gas, often discourages obtaining information which is vital for evaluation of well performance. Field tests have verified the accuracy of a sensitive, high-pressure acoustic instrument that enables determination of fluid levels and/or echo-time to a downhole marker, without limitation by depth, well tubulars or environment. This has opened the way for development of a diagnostic technique giving information about well pressures and fluid distribution in the wellbore without the use of downhole pressure survey tools. This Wellsite Pressure Calculation System (WPCS) is especially applicable for hostile environments, attributable to high pressure/high temperature, sour gas production, where wireline surveys involve significant risk and expense. Results, supported by field tests involving pressure buildups under controlled conditions, indicate the calculated pressures agree with those measured by downhole pressure bombs to within the accuracy of the pressure bombs (1%) and can be used satisfactorily in buildup analysis. A description of three sets of field tests is given, as well as the development of programs for wellsite data analysis using a portable, battery-powered microcomputer.