Profiling Horizontal Oil/Water Production

Abstract

Summary Flow loop evaluations show that some wireline logging tools aresignificantly limited in profiling segregated horizontal oil/water flows. Theevaluations also identify one tool combination that is suitable for segregatedas well as mixed flows and demonstrate the profiling accuracy of thiscombination in both flow types. Introduction. This paper describes results of a project to evaluate the capabilities ofproduction logging instruments for profiling oil/water flows in a 4-in. IDproduction logging instruments for profiling oil/water flows in a 4-in. IDhorizontal pipe. In profiling, the principal objective is to determine theindividual flow rates of oil and water at a selected depth in an oil/waterflow. these individual rates can be determined from the total flow rate and thewater cut at the depth, two values that must be estimated from logginginstrument measurements. The water cut expresses the flow rate of water as afraction of the total flow rat e; thus, the flow rate of water is thearithmetic product of the total flow rate and the water cut. The flow rate ofoil is the total flow rate diminished by the flow rate of water. The objectiveof this Sect was to evaluate commonly used production logging instrumentsquantiatively under controlled conditions in a horizontal pipe connected with asurface flow loop. In the horizontal 4-in.-ID pipe, a pronounced tendencytoward segregated flow exists at total flow rates <1,000 BID, as will bediscussed later. Fig. 1 shows a low water-cut, segregated flow, withwatermoving along the bottom of a pipe and oil moving above the water as aseparate phase. Also shown is a centered, nondiverting logging instrumentarranged to measure the properties of fluid now its centerline. In this case, the tool responds properties of fluid now its centerline. In this case, thetool responds only to the oil; it cannot respond to the water cut or total flowrate. Fig. 2 shows a segregated oil/water flow at high water cut with the sametype of logging instrument as shown in Fig. 1. In this instance, the logginginstrument responds only to the water and cannot respond to the water cut ortotal flow rate. One of the logging tools evaluated in the project was thediverting flowmeter (Fig.3) This flowmeter incorporates a diverting elementthat funnels the production flow into a narrow channel in the tool. Thediverted flow rotates a spinner element and then isdischaagedtotheproductionpipe. The spinner rotation rate is transmitted by thewireline to the surface, where it is recorded in revolutions per second. Asdiscussed later, the rotation value can be used to determine the total flowrate of an oil/water flow. Because the production flow is diverted into thenarrow channel where the flow moves at a much higher velocity as it rotates thespinner, the diverting flowmeter responds to the total flow rate in asegregated oil/water flow and in a mixed flow. The unfocused density tool, which includes a gamma ray source and detector Fig.4), was also evaluated. Gamma radiation intensity is measured at the detector and transmitted to thesurface by the wireline, where it is recorded as frequency. Note that someradiation paths investigate the well fluids, others the pipe wall, and stillothers the formation just outside the pipe. For this reason, the unfocuseddensity tool responds to the "bulk density" i.e., the density of thewell fluids combined with the density of the pipe wall and the formation nearthe pipe. Raising the concentration of water increases the bulk density andreduces the recorded frequency; raising the concentration of oil reduces thebulk density and increases the frequency. Source strength and source/detectorspacing can be adjusted so that 95% of the response of the unfocused densitytool results from the well fluids. This adjustment is preferred when theunfocused density tool is used to measure the water cut. Because itinvestigates the entire wellbore, the unfocused density tool responds to theoverall composition of the well fluids and hence is capable of responding tothe water cut in both segregated and mixed oil/water flows. Flow Loop Tests Fig. 5 shows the logging tool configuration used for the flow loopevaluations. The configuration included a diverting flowmeter at the bottom ofthe tool combination and an unfocused density tool near the discharge of theflowmeter. A focused density or a fluid capacitance tool was used when theunfocused density tool was not utilized. Logging tool responses for theevaluations were recorded simultaneously. P. 780