Patent Application
20090007650
“Bucket testing” is the current standard practice for verifying the accuracy and flow rates of a fluid delivery system for blending for downhole use. The equipment operator turns on the system and fills a 5-gallon bucket, checking the fill time with a stopwatch. The operator then compares the time on the stopwatch with an electronic readout from a flowmeter in that system. Bucket testing is a low-tech method of testing. Because the operator must rely on the stopwatch, and a subjective interpretation of when the bucket is full, bucket testing is likely to provide inaccurate readings. Further, when hazardous chemicals are involved, the operator and other personnel are exposed to corrosive, flammable, and/or toxic fluid. Additionally, bucket testing can be environmentally unfriendly and/or wasteful, since fluid must leave the system for this verification.
The present invention relates generally to the verification of properties of a fluid. More specifically, the present invention provides a method and apparatus for verification at a wellsite.
In one embodiment of the present invention, a method for wellsite verification of at least one property of at least one fluid comprises: providing a fluid delivery system at the wellsite; providing at least one reference meter at the wellsite; and measuring the property of the fluid within the fluid delivery system, using the reference meter. The measuring step may be performed prior to or during dispatch of the fluid into a well bore. The reference meter may be a high precision meter.
In another embodiment of the present invention, an apparatus for wellsite verification of at least one property of at least one fluid comprises: a fluid delivery system and at least one reference meter for measuring the property of the fluid within the fluid delivery system. In this embodiment, the fluid delivery system and the reference meter are both located at the wellsite. A trailer may support the fluid delivery system and the reference meter.
Referring now to
System meter 110 may be any type of meter typically used in a downhole operation. For example, system meter 110 may be a Coriolis flowmeter. System 100 may include tank 130 to initially hold the fluid, until pump 140 causes the fluid within tank 130 to flow out and into system meter 110. Fluid may then pass through first valve 150. First valve 150 may be any of a number of different valves. For example, it may be a 3 way ball valve with one outlet that allows fluid to flow toward check valve 160, and an alternative outlet that allows fluid to flow toward reference meter 120. After passing through reference meter 120, fluid may flow through second valve 180, into tank return 190 or to check valve 160.
Reference meter 120 may be removably attached to system 100 via first dry disconnect 200 and second dry disconnect 210, allowing reference meter 120 to be taken completely off line for inspection and/or recalibration. Reference meter 120 may be independent of the fluid delivery system. Reference meter 120 may be a Coriolis or any other type of reference meter suitable for use with the specific fluid and for the specific properties for which measurement is desired. In any event, it is desirable that reference meter 120 be suitable for use at the wellsite. One purpose of reference meter 120 may be to establish the performance accuracy of system meter 110 to some tolerance. For example, reference meter 120 may be a high precision meter which has been calibrated and accuracy documented by a competent authority certificate. Reference meter 120 may also be certified for structural integrity. Documentation may follow reference meter 120 with information as to its accuracy, who performed the testing and calibration and when the last test was performed. For certain applications, reference meter 120 may also meet Zone 2, ATEX guidelines for equipment used in hazardous area environments and be certified as such. Each reference meter 120 may be physically tagged for its overall accuracy, mass accuracy, density accuracy, meter serial number and date of calibration. Also on the tag may be the institute whose standard was used for calibration. For example, the tag may indicate National Institute for Standards and Technology (NIST). In another embodiment, reference meter 120 may be tagged for sensor serial number, transmitter serial number, calibration date, calibration standard institute, flow accuracy, density accuracy, and repeatability.
Some exemplary reference meters are covered in the American Petroleum Institute Manual of Petroleum Measurement Standards. In particular, Chapter 4 deals with “proving systems,” section 5 deals with “master-meter provers.” In this embodiment, reference meter 120 has a calibration that has been determined against a standard before it is installed in series with system meter 110, and comparative readings are taken. While reference meter 120 may be a derivation of a master meter prover, reference meter 120 may alternatively be any type of reference meter, including a mechanical displacement prover (“pipe prover”) or a positive displacement meter, such as those used for crude oil and petroleum products. Liquid provers, and more specifically pipe provers allow for in-place testing of system meter 110, including the fluid and the flow effects in system 100.
Check valve 160 may be provided to prevent back flow of other process fluids into the fluid delivery system of system 100. Check valve 160 may be any type typically used in a stimulation operation. As shown in this embodiment, check valve 160 flows into process line 170. However, check valve 160 may flow into any of a number of lines.
In an exemplary embodiment, the operator takes measurements using system meter 110 and compares them with measurements taken using reference meter 120. Desirably, this is done prior to dispatching the fluid into the well bore. However, comparisons may be made during dispatch, or after the fluid is downhole, with any required adjustments to pump 140, or any other component of system 100 taking place as soon as practical, under the circumstances. While measurement of flowrate is most common, system 100 may also be used to measure density and/or specific gravity.
Referring now to
Reference meter 120 may be used with any existing chemical additive system, in which case reference meter 120 is added to the existing system to alleviate the need for bucket testing. This creates a safer, more accurate, and more environmentally friendly system. System 100 may be used for verification in any type of onsite oilfield operation, such as, but not limited to, acid blending and mixing, blending or mixing for fracturing chemicals, or any other chemical blending operation. System 100 may be used in a number of different applications where bucket testing is currently used, including stimulation, mudding, and cementing operations. More specifically, system 100 may be used for fracturing and/or acidizing operations.
System 100, and more particularly reference meter 120 may be placed wherever a meter is typically used, including within an on-the-fly mixing operation. In this type of operation, system 100 is desirably be used prior to mixing the chemicals. However, system 100 may alternatively be used during mixing.
The procedure, process, or system for verifying a fluid delivery system accuracy for oilwell stimulation fluids that involves reference meter 120 may apply to any application where chemicals are required to be added into a blending or mixing process. For example, a blending process where one or more liquid additives must be metered into a blended fluid or device for blending the fluid and where the system meter and/or pump must be verified for accuracy. Some applications may include, but are not limited to, oilfield stimulation blenders, liquid additive delivery trucks, trailers, and/or skids. Other applications may include any process where a “bucket test” is the current standard for verifying accuracy of the fluid delivery system. For example, liquid additive systems for offshore applications. In this case, a skid may replace trailer 230 and a stimulation vessel would attach to a platform.
The procedure, process, or system involving reference meter 120 may also apply to applications where chemicals are being transferred from one liquid additive system to another. For example, transferring liquid additives from one container to another regardless of whether the containers are within one fluid delivery system or other fluid delivery systems.
Reference meter 120 may also be used as a backup to system meter 110, which may be a standard fluid delivery meter installed into a fluid delivery system.
Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. For example, while system meter 110 is shown between pump 140 and reference meter 120, system meter 110, and reference meter 120 could each be placed in any of a number of locations. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the present invention. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee.
