An earlier publication has discussed three methods for obtaining relativepermeability data on small core samples and the apparatus and technique for thecapillary pressure displacement method. This paper describes the apparatus andtechnique for the solution gas and the dynamic displacement methods andpresents a routine procedure for obtaining oil-gas and water-oil relativepermeability data. Theoretical and experimental considerations are presented to show that theend effect commonly associated with the dynamic flow mechanism is extremelysmall where constant rates are employed in the flowing phase. An effect of flowrate on relative permeabilities obtained by the dynamic system is found onlywhen gas is one of the flowing phases and this effect is ascribed to a form ofchanneling in the capillary system. The apparatus and procedures used to obtain relative permeability data withthree phases flowing are described and some preliminary results of the use ofthis method are shown. Introduction In a previous publication from this laboratory there appeared a briefdiscussion of the concepts behind three basic methods for obtaining relativepermeability data. These three methods were called the capillary pressuredisplacement method, the solution gas displacement method, and the dynamicdisplacement method - the names being suggestive of the type of process usedfor obtaining the desired saturation prior to making the permeabilitymeasurements. In the same publication, the apparatus and technique for thecapillary pressure displacement method were described and some typical resultsobtained by this method were presented. This paper will present:The routine procedure used to obtain permeability data on small coresamples flowing;The experimental techniques for the solution gas and dynamic displacementmethods for obtaining relative permeability data;The results of some studies on the mechanism of fluid flow throughconsolidated porous media; and,The preliminary results on the determination of relative permeability for asystem in which three phases are flowing. T.P. 3056

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Summary Afterflow measurement identifies downhole problems as indicated by the presence of (1) a long fluid column, (2) U-tubing of liquid from the tubing to the annulus, (3) gas coning, and (4) stratification, as evidenced by highpressure gas stringers or high-pressure liquid stringers. Introduction Pumping wells are generally older wells with declining production. They are prime candidates for estimation of skin damage, fracture length, reservoir pressure, effective permeability, and other diagnostic information provided by pressure buildup curves. However, the necessity of removing the rods and pumps to place the conventional pressure bomb and then temporarily replacing the rods and pumps to restabilize the well and get the flowing bottomhole pressure, which is essential to well damage estimates, has meant that buildup curves practically never were run on pumping wells.We have been getting buildup curves on pumping wells by determining the liquid level in the annulus acoustically, measuring the surface annulus pressure, and calculating the sandface pressure. This permits following the liquid level and bottomhole pressure before shut-in to check pump operation or well stabilization and then following the buildup from the moment of shut-in. This also gives direct measures of the well storage factor and the afterflows of gas and liquid during buildup. Calculation of Bottomhole Pressure, Afterflows, and Well Storage A schematic of a typical well configuration is shown in Fig. 1. There is no packer. The gas and liquid entering the well separate in the annulus, the gas rising up through the fluid column to be produced out of the wing valve and the liquid being pumped out through the tubing.Our well sounder has a three-way valve that maintains a pressure above the annulus pressure in an expansion chamber. Upon signal from a preprogrammed self-contained monitor, a pulse of nitrogen from the expansion chamber enters, the annulus, starting a counter. The returning echo from the fluid stops the counter. The speed of the counter is adjusted by a dial calibrated in acoustic velocity. When setting up, we measure the liquid depth with a collar counting device and adjust the counter speed to give feet depth to liquid directly. Under favorable conditions, our reproducibility is about 1 ft. The setting on the acoustic velocity dial gives the acoustic velocity of the gas in the annulus. Knowing the acoustic velocity, we calculate the specific gravity of the gas in the annulus and its Z factor. Knowing the surface pressure, the annulus area, the depth to liquid, and the Z factor at each point along the curve, we can calculate the gas column weight to get the average pressure in the gas and the standard cubic feet of gas in the annulus at each point. The increase in this gas between successive points directly gives the Mcf/D flowing into the gas space during each time intervalthe gas afterflow.The sandface pressure is calculated starting with the measured surface pressure. The weight of the gas column is calculated by integration knowing the gas gravity, temperature, and average Z factor. This gives the pressure at the top of the fluid column.The weight of the fluid column is calculated stepwise. starting at the top, a depth interval is taken such that the pressure at the bottom of the interval will be 1.2 times the pressure at the top of the interval. The average pressure is 1.1 times the pressure at the top of the interval, the annulus area is known, and the rate of gas flow is the previously measured gas afterflow. From these three data, published correlations give the fraction of liquid in the interval. JPT P. 397^

The possibility has been mentioned that large pressure gradients in a solution gas driven field caused by high production rates might lead to a reduction in the ultimate recovery obtainable compared to that which would be obtained by a very slow rate of production. In the present study the reservoir conditions accompanying a high rate of production and the corresponding ultimate recovery were compared with those obtained if the reservoir were produced at some marginal rate throughout its entire life. The method of calculation invoh-ed the application of fluid flow -material balance analysis to a series of successive steady state conditions in the reservoir. In the case studied very little difference in recovery was obtained at the abandonment pressure. An analysis of the basic factors involved indicates that the same results would hold for considerable variation in properties of reservoir fluids, permeability of the formation or well spacing. Even if the reservoir has a water drive it appears that no harm wiII be done by open flow production if the rate is cut back before any appreciable free gas is produced. However, any condition which leads to disproportionate withdrawal rates and which causes large pressure differences over large areas might result in substantial loss in ultimate recovery.

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