COPYRIGHT. Production Logging Flowmeter Survey Solution Guide

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1 Production Logging Flowmeter Survey Solution Guide Applying Slippage & Liquid Holdup equations, solve for Q oil and Q water at 6130 ft and ft, the % ratio of flow is about 100 %, or ft, the % ratio of flow is about 13.1 % or about x 9190 = 1204 BFPD WATER HOLDUP = Yw = (ρt - ρo) / (ρw - ρo) where ρ is fluid density : t = local from log, w = water; o = 6130 ft, water holdup = ( ) / ( ) = 6216 ft, water holdup = ( ) / ( ) = From 6130 ft slippage velocity Vs = 20 ft/min for (ρw -ρo) = ( ) To get Q in 6216 ft slippage velocity Vs = 12.1 ft/min for (ρw -ρo) = ( ) Pseudo-Area = 1.78 (ID csg 2 - OD tool2 ) = 1.78 ( ) = 6130 ft : Qo = (1 - Yw) (Qt +Vs A Yw) Qo = ( ) ( ( )) = 7097 BOPD Qw = = 2093 BWPD Conversion factor 1.78 resolves 6216 ft : Qo = ( ) ( ( )) Qo = 674 BOPD Qw = = 530 BWPD

2 Production Logging Flowmeter Survey Interpretation

3 Production Logging Threshold Velocity An actual cased hole log has been filed without interpretation during summer of Several years afterwards, the same well is showing a declining performance. An assessment history of the well past performance is needed to diagnose the current status from observations and possibly prepare remedial action. The essential data available from the old log are copied in the next pages. In 1983, CPI logs were not available. Make up for the backlog of data gathering. Browse through data and answer the following questions. Questions 1 Is this well located onshore or offshore? Offshore 2 Is this well vertical or deviated? Deviated 3 What is the status of this well? Water Injection well 4 What are the depths MD of the perforated zones in this well? m m (Zone CE) m m (Zone CT) m 3063 m (Zone D1) 5 What is the total depth TMD of this well? 3096 m 6 What logs have been run? CFM (Continuous Flowmeter), HRT (High Resolution Thermometer), MAN (Manometer) 7 Would a Gradiomanometer add value to the information? No, the gradient is known (water injection) 8 Calibrate tool (use blank chart provided). 9 Determine threshold velocity fpm 10 Determine full downhole flowrate in 7 (17.8 cm) casing, if at all possible bpd 11 Determine total flowrate and percentage flowrates per zone bpd 12 Provide comments, conclusions and recommendations. Need to check discrepancy between measured downhole flowrate and surface readings. Notes 1 As seen on the left scale, the logging runs have been performed with depth being measured in meters, while the blank calibration chart bears tool velocity units in ft/min. 2 Cross check the cable speed indications on the right track of logs. 3 Whenever flowmeter scale is absent from the right track, assume it to be 0 40 RPS. 4 Observe where the recordings have been made by comparing with well completion sketch. 1

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7 Production Logging Logging Anomalies in Deviated Hole A high deviation well has been drilled, penetrating a thick carbonate reservoir with multiple sub zones. Following the results of Open Hole Logs, the reservoir was perforated with 4 casing guns at 4 spf. After an acid job, clean up and flow test, the well was shut in for 28 hours and the PCT (Production Combination Tool) was run. The tool was consisting of: FBS Continuous Flowmeter GM Gradiomanometer MAN Manometer HRT Thermometer The well completion sketch is attached in the data section. A composite log is illustrated. Over the zone, the following surveys were performed. WELL SHUT IN Flowmeter: 6 passes UP, 6 passes DOWN Gradiomanometer : 2 passes UP, 2 passes DOWN Manometer: 2 passes UP, 1 pass DOWN Temperature: 1 pass UP, 2 passes DOWN WELL FLOWING Flowmeter: 6 passes UP, 6 passes DOWN Gradiomanometer: 2 passes UP, 2 passes DOWN Manometer: 2 passes UP, 2 passes DOWN Temperature: 2 passes UP, 1 pass DOWN FLOWMETER IN SITU CALIBRATION A zero flow calibration was performed. The zero passes includes the perforated intervals. The plot yields all points in good agreement and gives the threshold velocity: V t = 5 ft/min A close inspection of the flowmeter profiles, not included here, confirms that there is no apparent internal cross flow while the well is shut in. 1

8 GRADIOMANOMETER The gradiomanometer (see log) pinpoints the borehole water contact (OWC) at 8770 ft. The downhole density reading for the oil column is g/cc (uncorrected). THERMOMETER The temperature recordings show that the well has not been shut in long enough to reach back to geothermal gradient. Production also appears to be at a temperature higher than geothermal and a hot sink appears to exist from 8770 to 8790 ft. FLOWMETER FULL 8700 ft Flowmeter passes have been recorded, 8 of which are (partly) figured in the data section. The full flow calibration yields a total downhole flowrate above perforations: Q twf = 1780 BPD It is immediately apparent that oil is flowing at this point because: There is no water production at surface conditions: Q wsc = 0 The flowing and shut in gradio recordings are identical over this interval Thus, Q twf = 1780 BPD Given that FVF = Bo = 1.164, we can compute Q osc = 1780/1.164 = 1530 BPD which compares favorably with the actual surface production rate, which was estimated to be 1400 BPD during the PCT operation. GRADIOMANOMETER The flowing gradio readings reveal that: There seems to be some oil production from the lower perforations. The amplified gradio shows a decrease at 8788 ft. Up to 8740 ft, the gradio recordings look noisy, which is a standard in the case of oil bubbling through a standing water column. The OWC has been lifted up from 8770 ft to 8735 ft. Above this depth, the oil bubbles coalesce to single phase oil production. The OWC position in the well is a function of the production rate. FLOWMETER 8770 ft The flowmeter recordings consist of a total of 12 passes, 8 of which are partly reproduced in the attachments. Obviously, any readings obtained below the zero flow depth are indicative of flow in the opposite direction to the one that we expect from well observation. 2

9 As this is a production well, flow is, by definition, in the upwards direction. A calibration plot of the anomaly reveals an apparent example of downflow. The points are all in good agreement, providing reliable calibration lines. The standard calculation yields the following values: UP passes: DOWN passes: 5208 BPD 4635 BPD These values are in relatively good agreement, considering the logging conditions. However, this apparent cross flow does not seem to be realistic There is no indication of cross flow when the well is shut in The reservoir pressure is well known and the possibility of a such a large cross flow is ruled out. CONCLUSION It is known that diphasic flow patterns in highly deviated pipes are anomalous. If a flowmeter is placed in such a pipe with inadequate centralization, it is likely to read a downward flow. Since oil slippage increases with well inclination, the apparent holdup also increases. Thus, quantitative evaluations using standard procedures will lead to erroneous results. In this particular case, Special centralization techniques were used The flowmeter readings in full flow look normal The threshold value is realistic The calculated flow rate compares with the surface value. If all indications point out to good centralization over the full flow zone above perforations, it seems reasonable to assume that centralization will still be good 50 ft deeper. The tool centralization appears good and excentralization is not a cause to reading anomalies. At bottom hole, below the level where the water hold up recedes to a steady state value, a flowmeter will is likely to be in error and record turbulence effects and downward flow. 3

10 ZERO FLOW 8700 ft 4

11 C O PY R IG H T FLOWMETER 8700 ft 5

12 FLOWMETER 8770 ft 6

13 CONCLUSION 7