SYSTEM FOR OPTIMIZATION OF HYDROCARBON PRODUCTION

Abstract

Monitoring system for a well stream from at least one hydrocarbon well with seawater injection, wherein the monitoring system is connectable to a well stream sample point for receiving a sample of the well stream, wherein the monitoring system comprises a sample receiving system, a sample preparation system and an analysing system;—wherein the sample receiving system comprises:—a fluid conduit connectable for fluid communication with the well stream sample point and—a separator for separating a water fraction from a well stream sample;—wherein the sample preparation system comprises a filter for filtering the separated water fraction; and—wherein the analysing system comprises an x-ray fluorescence analyser for measurement of the concentration of at least one of the following dissolved elements Fe, Ba, Ca, S, Cl, P, Cu, Zn, Pb, Br or scale inhibitor tracers in the filtered water sample; wherein the monitoring system comprises at least one of the following pressure control and measurement systems: a first a pressure control and measurement system connected to the sample receiving system, a second pressure control and measurement system connected to the sample preparation system.

Claims

1. Monitoring system for a well stream from at least one hydrocarbon well with seawater injection, wherein the monitoring system is connectable to a well stream sample point for receiving a sample of the well stream, wherein the monitoring system comprises a sample receiving system, a sample preparation system and an analysing system; wherein the sample receiving system comprises a fluid conduit connectable for fluid communication with the well stream sample point and a separator for separating a water fraction from a well stream sample; wherein the sample preparation system comprises a filter for filtering the separated water fraction; and wherein the analysing system comprises an x-ray fluorescence analyser for measurement of the concentration of at least one of the following dissolved elements Fe, Ba, Ca, S, Cl, P, Cu, Zn, Pb, Br or scale inhibitor tracers in the filtered water sample; wherein the monitoring system comprises at least one of the following pressure control and measurement systems: a first a pressure control and measurement system connected to the sample receiving system, a second pressure control and measurement system connected to the sample preparation system.

2. System according to claim 1, wherein the sample receiving system comprises a sample receiving vessel having a volume size large enough to receive a statistically significant sample volume to do statistically significant measurements of said dissolved elements, preferably the volume is in the range of 25-500 ml.

3. System according to claim 1, wherein the sample preparation system comprises a sample accumulation and circulation tank sized and arranged to receive the filtered sample and to circulate the filtered sample multiple times passed the XRF.

4. System according to any one of the previous claims, wherein the XRF analyser is fluidly connected to at least one calibration liquid tank comprising a liquid with a standard concentration of one compound readily identifiable by the XRF for calibration or verification, or both of the XRF measurements.

5. System according to claim 4, wherein the system comprises a recycle conduit for recycling at least a portion of the analysed liquid of standard concentration of one compound readily identifiable by the XRF back to the at least one tank.

6. System according to claim 1, wherein the monitoring system comprises at least one of the following temperature sensors: a first temperature sensor connected to the sample receiving system, a second temperature sensor connected to the sample preparation system.

7. System according to claim 1, wherein the system comprises data processor and the XRF analyser measures the ion concentration of Cl in the sample, and the data processor uses the measurement to calculate the seawater fraction of the produced water in the well stream.

8. System according to claim 1, wherein the monitoring system further is a scale monitoring system, wherein the x-ray fluorescence analyser monitors the concentration of chloride and barium ions in the water fraction.

9. System according to claim 1, wherein the analysing system further comprises a Fourier Transform Infrared Spectroscopy analyser, or any other suitably applicable measurement instrument, for determining the concentration of scale inhibitor in the filtered water sample.

10. System according to claim 1, wherein a FTIR analyser is in a fluid connection downstream to a separated hydrocarbon outlet to monitor the types and concentration of asphaltenes in the hydrocarbons from the well sample.

11. System according to claim 1, wherein the system comprises a high speed high quality camera or video window exposed to fluid from the sample preparation system, especially a retentate fluid from the filter, such that the camera or video can capture pictures of particles, wherein data from the captured pictures is applicable for calculating the particle type, size and distributions, i.e. applicable for determining the produced water solids concentration, composition and morphology.

12. System according to claim 9, wherein the FTIR analyser further monitors at least the concentration of one of the following components: mono ethylene glycol, triethylene glycol, methanol, kinetic hydrate inhibitors, water, amine, organic acids, or BTEX (benzene, toluene, ethylbenzene and xylenes).

13. System according to claim 1, wherein the system is for monitoring more than one hydrocarbon well and is adapted to selectively receive samples from the hydrocarbon wells.

14. System according to claim 1, wherein the filter restricts particles larger than between 0.1-20 μm from entering the analyser system.

15. System according to claim 1, wherein the sample preparation system comprises a further separator, with an inlet in fluid communication with the separator of the sample receiving system, and an outlet in fluid communication with the filter.

16. System according to claim 1, wherein the sample preparation system comprises a sample accumulation tank for accumulating the sample.

17. System according to claim 1, wherein the analysing system comprises a data processor in communication with the analyser(s) for processing the analysis results determining the seawater fraction.

18. System according to claim 17, wherein the data processor further is in communication with one or more production well valves and/or seawater injection well valves such that the production of hydrocarbons and/or injection of water is regulated based on the monitoring.

19. System according to claim 1, wherein sample receiving system further comprises at least one pH-sensor.

20. System according to claim 1, wherein the monitoring system is a remotely operated vehicle that is remotely operated fluidly connectable to the well stream sample point.

21. Method for monitoring the well stream from a hydrocarbon well, wherein the method comprises passing a sample of the well stream to a sample receiving system reducing the pressure of the sample, separating a water fraction from the sample, filtering the separated water fraction and passing the filtered water fraction through a flow cell with a x-ray fluorescence analyser connected thereto, thereby measuring the concentration of at least one ion in the sample.

22. Method according to claim 21, wherein the XRF analyses the content of chloride and the method comprises calculating the seawater fraction in the well stream.

23. Method according to claim 22, wherein the results of the monitoring forms the part of the basis for adjusting injection of water in a water injection well.

24. Method according to claim 21, wherein the XRF analyses the content of chloride and barium ions and the method comprises calculating if the concentration of barium ions is reduced due to scaling, and wherein the method further comprises determining the need for initiating a scale inhibitor squeeze based on the results of the monitoring.

25. Method according to claim 21, wherein the method further comprises passing the filtered water sample trough a flow cell with a Fourier Transform Infrared Spectroscopy analyser for measuring the concentration of dissolved scale inhibitor in the water sample.

26. Method according to claim 21, wherein the method comprises accumulating the filtered sample in a sample accumulation and circulation tank and circulating the filtered sample multiple times passed the XRF, or so that it is passed by the XRF for 1-60 minutes.

27. Method according to claim 21, wherein the method comprises calibrating or verification of the XRF analyser by passing a liquid with a standard concentration of one compound readily identifiable by the XRF is through the XRF flow cell.

28. Method according to claim 27, wherein the method comprises recycling at least a portion of the analysed liquid of standard concentration of one compound readily identifiable by the XRF from the flow cell back to at least one calibration liquid tank (100).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0074] The enclosed figures are schematic illustrations of the invention or parts thereof. The figures are prepared with the intention to illustrate the connections between the different units. The figures are not drawn up to illustrate the size or exact position of the different equipment.

[0075] FIG. 1 is an overview of subsea hydrocarbon wells and a system according to the present invention.

[0076] FIG. 2 is an overview of the monitoring system.

[0077] FIG. 3 is a graph showing the chloride content depending on seawater fraction.

[0078] FIG. 4 is a graph showing the barium content as a function of seawater fraction, calculated based on dilution and as measured in case of scaling taking place.

PRINCIPAL DESCRIPTION OF THE INVENTION

[0079] The present invention will now be discussed in further detail with reference to the enclosed figures showing an embodiment thereof. A person skilled in the art will appreciate that some illustrated features are optional and that although only one embodiment is illustrated the invention is not limited to this specific embodiment.

[0080] To establish knowledge of the composition of the formation water baseline measurements are performed before the injection water reaches the production well. These measurements include measuring formation particle content and ion content of the formation water.

[0081] FIGS. 1 and 2 illustrate an embodiment of the system.

[0082] FIG. 1 shows the seabed 2 with two production wells 3, 3′ with production valves 4, 4′ and two water injection wells 18, 18′ with valves 24,24′. From the production wells the well stream is during production past through valve 4,4′ and squeeze valve 5, 5′ through well stream conduit 7, 7′ respectively to the manifold 8 with valves 6, 6′. From there the combined well stream is passed to a separator 10 providing a gas stream 11 and/or a liquid hydrocarbon stream 13 and produced water 15. Prior to entering the manifold 8 well stream sample point 31, 31′ are connected to the respective well stream 7, 7′ for withdrawing samples therefrom.

[0083] The separator 10 separates the well stream in a gas stream 11, an initial liquid hydrocarbon stream 13 and a produced water stream 15. The produced water may be reinjected, and the water outlet of the separator 10 is connected via pump 9 and conduit 17 with the injection wells. The separator 10 and pump 9 may be arranged topside or subsea. The ion content of the produced water for reinjection is known from the Online Scale Monitoring System, OSM 1.

[0084] In the illustrated embodiment the produced water 15 is used for reinjection. Via produced water pump 9 and conduit 17, 17′ and valves 19, 19′ it can be reinjected. Preferably, flowmeters are connected close to the valves 19,19′ measuring the amount of produced water being reinjected. This information is supplied to the data processor and controller 50. The salt content and scale inhibitor content of the reinjected produced water is known from the monitoring system. From seawater treatment unit 22 seawater is provided via valves 28, 28′ and conduits 27, 27′. Seawater treatment units are well known and may include sulphur removal units and different filtering such as RO. The seawater treatment unit 22 further comprises equipment for measuring, estimating, calculating the content of SO.sub.4.sup.2− and other ions.

[0085] From the scale inhibitor tank 20 scale inhibitor may be added to the injection water via pipelines 23, 23′ and valves 26, 26′. The scale inhibitor conduits 21, 21′ and valves 25, 25 are used for squeezing. During squeezing the production is stopped and valves 5, 5′ closed before the scale inhibitor is injected.

[0086] The key components of the Proactive/Adaptive OSM system 1 are given below:

[0087] 1) Three Phase Sample Tapping at High Temperature and Pressure [0088] Tapping at Individual Wells but the Sample is Sent to One or Multiple Sample receiving/preconditioning vessel 34 via valves 32, 32′ and well stream sample pipeline 33.

[0089] 2) Sample Receiving System [0090] Pressure let down to 1 to 5 bars in the system, this can be done in two stages first reduction in the sample receiving system and optionally a second pressure adjustment in the sample preparation system. The system includes level control and separate gas outlet 35 to ease the control of the pressure reduction. The gas can, as illustrated, via gas valve 36, be passed into waste collection tank 46. T1 and P1 are temperature and pressure sensors for controlling the depressurisation process. [0091] The method preferably includes using the high-pressure samples from the sampling point to rinse the content of the system with the fresh sample for a duration equivalent to the through flow of at least 3 times the liquid volume in this vessel. This will make sure that new representative sample is collected for further analyses. A typical normal sample size is 25 ml, but to achieve statistical significant measurement the total sampling volume can be multiple times this sample size volume. In one embodiment of the invention the total sampling volume is larger than 2 times the typical normal sample size, in another embodiment sampling volume is 1.01-20 times the typical normal sample size, in another embodiment the total sampling volume is larger than 1.1 times the normal sample size. During this rinsing process the whole sample can be passed on to the top side or closed drain as appropriate. [0092] Once the sample volume is collected, the sample is degassed and while degassing, routing the gas to topside process, which is preferably at a pressure lower than the pressure in the sample receiving vessel or to waste tank as illustrated. [0093] Sample receiving system 34 may include pressure reduction and phase separation equipment, such as gravity separator, a cyclone, an Induced Gas Flotation. The system 34 is equipped with level control and a temperature sensor T1 and pressure sensor P1. The information on the pressure and temperature is transferred to the data processor 98, the data transfer lines are omitted on the figure for clarity reasons. [0094] After degassing, a residence time in the separator (5 to 30 min) to have hydrocarbon (HC)-water separation is allowed. [0095] This separator/vessel 34 is preferably equipped with a interface level measurement instrument. After HC-water separation, a water sample is pumped from this separator 34 via valve 41 to the sample pre-conditioning/preparation system 50 located close to the XRF and FTIR analyser. Tapping of the sample is below the HC-water interface and approximately halfway into the water phase. This will minimize any settled solids being transferred to the sample pre-conditioning system 50. [0096] The separator 34 is equipped with waste outlets connected via valves 38 and 40 with the waste collection tank 46. The different streams are collected in the waste collection tank 46 equipped with level control. Liquid can be removed from the waste tank 46 via pump 52 as stream 53. Gas is vented from the waste tank 46 as stream 49 via valve 51.

[0097] 3) Sample Pre-Conditioning/Preparation System 50 [0098] This system in one embodiment consists of [0099] a pre-conditioning vessel 42 to collect the sample from sample receiver vessel/separator 34, [0100] a preferably regenerable filter 72 to remove any solids larger than 20 μm, preferably lager than 10 μm, more preferably larger than 1 μm, or larger than 0.1 μm, present in the water sample, [0101] vessel(s) for chemical cleaning reagents (CIP) 64 connected to the outlet stream from vessel 42 via line 61 and valve 62. [0102] In the illustrated embodiment all waste streams are collected in one vessel 46 and pumped from there via pump 52 and line 53 to further handling. [0103] A sample accumulation tank 86. [0104] The system provides for using fresh high-pressure samples from the sample receiving vessel to rinse the content of the sample preconditioning vessel 42, for a duration equivalent to a flow of at least 3 times the liquid volume in this vessel. This will make sure that new representative sample is pumped for analysis. During this rinsing process the whole sample can be passed on to a waste collection vessel 46 or to a closed drain as appropriate. [0105] In one embodiment the system allows for further separation of the HC-water phases in the sample preconditioning vessel 42 with a residence time of 5 to 30 min. the vessel 42 has an outlet 47 connected to the waste collection tank via valve 48. T2 and P2 are temperature and pressure sensors respectively for controlling the process. [0106] This sample preconditioning vessel 42 is preferably also equipped with an interface level measurement instrument. After HC-water separation, the water sample is pumped from this vessel 42 via valve 66, sample conduit 63, sample pump 70 conduit 65, valve 68, filter 72 valve 74, and conduits 71, 81 to the flow cells 90 and 94 located at the XRF and optionally FTIR analysers respectively. Tapping of the sample is below the HC-water interface and approximately halfway into the water phase, this will minimize any settled solids being transferred to the flow cell. [0107] The collected/removed solid particles are sent to the waste tank 46 via retentate conduit 55 and retentate valve 54. [0108] This system will advantageously have at least one tank 64 for a scale removal/cleaning reagent; organic acids for carbonate scale removal and chelating agents like EDTA for sulphate scale removal. The bypass conduit 67 may be used for the cleaning circuit. By opening valve 76 and closing valves 68, and 78. If necessary, after having filed the analysis system 80 with cleaning fluid valve 66 and 54 may also be closed allowing the cleaning fluid to circulate. Opening valves 66 and 54 again the filter 72 will be backwashed with the cleaning fluid. [0109] Upon scaling or fouling of the flow cell window or the FTIR probe, cleaning reagents can be circulated in a closed loop to clean the flow cell window and tip of the FTIR probe. Spent cleaning agents can be drained to the waste collection vessel 46. Content of this waste collection vessel 46 can be subsequently pumped by pump 52 to produced water treatment system or closed drain at an appropriate frequency. [0110] The instruments of the XRF 90 and if present the FTIR 94 are separated from the fluid by a window in the respective flow cells. The windows can be made of glass or synthetic diamond, or “glassy carbon material”. [0111] The accumulation tank 86 allows for the sample to be analysed several times as the return line 83 via valve 82 transfers the analysed sample to the tank 86. From the tank 86 if valve 88 is open the sample is pump and filtered and returned to the flow cells, 90, 94.

[0112] 4) Online Analysis of the Pre-Conditioned Sample [0113] Online XRF analyser 92 [0114] Enables online, nearly real time analysis of the ionic composition of the produced water [0115] Ba, Ca, SO.sub.4, Cl, P and other ions can be analysed [0116] Profiling the measured chloride concentration in the produced water sample from individual wells. [0117] Estimating the dilution of the formation water by seawater injection, based on the chloride concentration in the formation, seawater and flow rates of respective streams. [0118] Estimate concentration of Ba, Ca, SO.sub.4 that corresponds to the dilution of the formation water with seawater and compare it with the actual measured concentration in the produced water. [0119] When measured concentration of the Ba, Ca, SO.sub.4 in the produced water per well is lower than what corresponds to dilution, this gives an indication that precipitation/scaling has happened for sulphate-based compounds. [0120] Analysis of the solid samples collected in the sample pre-conditioning filter 72 can be triggered and performed by XRF analyser 92. [0121] FTIR based spectrophotometry [0122] Enables near real time analysis of the produced water for scale inhibitor, especially organo-phosphonates, BTEX (benzene, toluene, ethylbenzene and xylenes) etc. [0123] The flow cell 90 of the XRF analyser 92 is fluidly connected to at least one calibration liquid tank 100 via calibration liquid conduit 101 and calibration liquid valve 102. The calibration liquid tank 100 comprises a liquid with a standard concentration of at least one compound readily identifiable by the XRF for calibration or verification, or both of the XRF measurements. In one embodiment the system may be adapted to recirculate at least part of the calibration liquid to the calibration liquid tank after a calibration. A separate return line (not shown) may be included for this purpose. [0124] Additionally, it is also possible to install/employ two monitoring systems in parallel, providing for calibration/verification by comparing the analysis results from the two systems. [0125] Disclosed on FIGS. 1 and 2 are also the possibility to analyse the particles from the formation. The filter 72 is under element analyses by the XRF 92 used to avoid particles in the flow cell 90. In this special operation mode the valves 66, 74 and 54 are closed and valve 57 and 76 are opened. The retentate stream 55 with collected particles from the filter 72 is passed via conduit 56 and the valve 57, pump 70 and filter bypass conduit 67 and inlet line 81 into the flow cell 90. Here the XRF is used to analyse the particles. After such a special operation the system is flushed to remove particles from the analysing system 80.

[0126] 5) Online Scale Prediction and Monitoring Tool [0127] The data processor 98 receives the analysis data, but also information on the baseline concentrations and flowrates of the system. [0128] Software enabling use of real time date from the XRF and FTIR analyser for predicting and monitoring the scale potential of the produced water for carbonate and sulphate scale.

[0129] 6) Digital Tool

[0130] The digital tool included in or connected to the data processor 98 provides: [0131] Visibility and availability of real time high quality data [0132] Produced water ionic composition—Ba, Ca, SO.sub.4, Cl, P [0133] Online monitoring of produced water chloride concentration to enable real time information about the dilution of the formation water chloride by seawater. [0134] Prediction of the dilution of the divalent ions (Ba, Ca, SO.sub.4) information that correspond to diluted chloride ions. [0135] Displaying any deviation in the measured divalent ions in produced water from the values that correspond to dilution. Reduction in the divalent ion concentration compared to dilution will indicate possible scale (BaSO.sub.4, CaSO.sub.4) formation. This could trigger filtering of the sample and characterization of the solids to ascertain the presence of (BaSO.sub.4, CaSO.sub.4) in the solids. [0136] Produced water scale inhibitor concentration [0137] Data analytics capability based on the availability of rich historical data [0138] Predictive and proactive scale squeeze management [0139] Optimized frequency of scale squeeze operation [0140] Optimized concentration of the scale inhibitor

[0141] The FIGS. 3 and 4 are provided to illustrate the results that can be obtained. FIG. 3 is an example of a chloride profile in the produced water due to mixing of the formation water from producing wells with injected seawater. The chloride content of the formation water is initially determined as a baseline. The chloride concentration of the injection water is also known and the linear relationship between them allows for the calculation of the line. Thereafter, any measurement of the chloride concentration in the produced water may via the established line be directly translated into the seawater fraction. For instance, if the measured chloride content is 27900 mg/l the seawater fraction is 30%. If the seawater fraction gets very high the well is primarily producing the injected water and of the HC content is going down at the same time the effect of the water injection may no longer be as beneficial.

[0142] FIG. 4 illustrates the situation with barium. The graph shows barium ion concentration profile in the produced water due to mixing/dilution of the formation water from producing wells with injected seawater (line) compared to possible actual barium ion concentration in the produced water (circles). Lower actual measured barium ion concentration in the produced water (compared to dilution line) indicates that BaSO.sub.4 precipitation has happened. Which means scaling is taking place and a squeeze should be initiate to avoid further scaling.

[0143] The system according to the invention allows for optimisation of the squeeze operations according to the analysis of the measurements, hence less squeeze operations would be required which results in less downtime of the production, furthermore with better control of scaling risk. Further, if the FTIR analyser is also included, this will provide additional information on the content of dissolved scale inhibitor in the produced water, providing an independent further indication of when a squeeze is required because the concentration is below the MIC level.

[0144] Furthermore, the system according to one preferred embodiment of the invention utilizes the measurements to optimize (minimize both scale risk and scale inhibitor consumption) the combined use of scale inhibitors in water injection at various water injection points, and scale squeeze operation at the various production wells at optimal periods of times during the production life time.

[0145] Furthermore, in one embodiment of the invention the ratio between formation water and water injection at the different sample points is measured, which is used to calculate the flow distribution from the water injection from the different water injection points, whereby the flow distribution information can be used to adjust the water injection flow rates at the different water injection points, and the production flow rates at the different wellheads, to optimize the production and minimize the scale risk.

TABLE-US-00001 Reference signs:  1 OSM—Online Scale Monitoring System  2 Seabed 3, 3′ Production well 4, 4′ Production well valve 5, 5′ Squeeze valve 6, 6′ Flow control valve 7, 7′ Well stream  8 Manifold  9 Produced water pump 10 Separator 11 Gas 13 Liquid hydrocarbon 15 Produced water 17 Reinjection conduit 18, 18′ Water injection well 19, 19′ Reinjection valve 20 Scale inhibitor tank 21, 21′ Scale inhibitor conduit 22 Seawater treatment unit 23, 23′ Scale inhibitor pipeline 24, 24′ Injection well valve 25, 25′ Scale inhibitor valve 26, 26′ Scale inhibitor pipeline valve 27, 27′ Seawater injection conduit 28, 28′ Seawater injection valve 31, 31′ Well stream sample point 32, 32′ Well stream sample valve 33 Well stream sample pipeline 34 Sample receiving system 35 Gas outlet 36 Gas valve 37 Separated hydrocarbon outlet 38 Separated hydrocarbon valve 39 Produced water waste outlet 40 Produced water waste valve 41 Sample valve 42 Sample preparation system 43 Gas outlet from preparation system 44 Gas valve on sample preparation system 45 Waste gas conduit 46 Waste collection tank 47 Waste conduit from sample preparation system 48 Waste conduit valve 49 Gas waste stream 50 Sample preparation system 51 Gas vent valve 52 Waste pump 53 Main waste stream 54 Retentate valve 55 Retentate stream with solids 56 Particle sample bypass conduit 57 Particle sample bypass valve 61 CIP conduit 62 CIP valve 63 Sample conduit 64 CIP solvent tank 65 Sample line 66 Prepared sample valve 67 Filter bypass conduit 68 Filter inlet valve 70 Sample pump 71 Filtered sample conduit 72 Filter 74 Permeate valve 76 Filter bypass valve 78 Accumulation tank inlet valve 80 Flow cell return valve 81 Sample inlet line 82 Analysing system 83 Sample return line 84 Sample inlet valve 86 Sample accumulation tank 88 Accumulation tank outlet valve 90 XRF flow cell 92 XRF 94 FTIR flow cell 96 FTIR 98 Data processor 100  Calibration liquid tank 101  Calibration liquid conduit 102  Calibration liquid valve