Drill stem tests (DSTs) are used to obtain (1) samples of the reservoir fluid, (2) measurements of static bottomhole pressure, (3) an indication of well productivity, and (4) short-term flow and pressure buildup tests from which permeability and the extent of damage or stimulation can be estimated. A shut-in time of 1 hour is usually preferred. The test must begin only after a liquid level stabilization period. Fax1-855-299-0792, Baseline Reduction Opportunity Program (BROA), Oil & Gas Software | Oilfield Software Solutions | Data Management. Operators assess the production potential of wells through several test methods, singularly or in combination. Based on data from these tests, engineers are able to determine production potential, skin and absolute open flow (AOF)the theoretical rate at which the well would flow if backpressure on the sandface, or the borehole wall, were zero. A quartz pressure gauge measures and records bottomhole pressures. Each test is designed to reveal specific information about a well. In either case, the gas is contained under pressure within the reservoir so that oil is pushed to the surface. During the production phase, well tests are aimed at monitoring reservoirs, collecting data for history matchingcomparing actual production with predicted production from reservoir simulatorand assessing the need for stimulation. Oilfield Review 2016. This can cause gas to break out of the fluid, which can throw the results of the test off. But the real power of well test data is their application to construction or correction of reservoir models, which allow operators to make better long-term decisions about their assets. Special Tests for Flowing Wells in Oil and Gas Production, Oil Well Testing (and Oil and Gas Production Allocation Software Simplified). Some oil and gas well testing can be quite specialized, but there are a few that youll almost certainly have to conduct. The pump should then be shut in so that the well bottom can fill with fluid once more. As mentioned above, reservoirs have to be under pressure for oil to be drawn from a well. Well and formation test data provide operators with information about their new and producing wells that is critical to making near-term operational decisions. The results of these sorts of tests are usually forwarded to some sort of regulatory agency, which will track the amount of gas produced and potentially set limits on the maximum amount of gas an operation is allowed to produce from the well over a given span of time. Its a test thats run on new wells or on wells that have been worked over. The tool isolates the formation from the mud column in the annulus. Since multi-point test data are available for virtually all gas wells, this method of analysis often proves to be a useful way of estimating permeability and skin factor, especially when drawdown or buildup tests are not available. Running productivity tests on a regular basis is important, as the well will change over time and adjusting your operations to match it is going to be necessary at some point. Testing on oil and gas wells may be performed at various stages of drilling, completion, and production for a variety of different purposes. Water can also provide the pressure that powers the well. Recently, testing has been made up of a combination of flow and shut-in periods and with greater complexity for well testing providing greater accuracy for volumes and understanding. If so, check out these related articles: How To Test Wells In Oil & Gas Production,Special Tests for Flowing Wells in Oil and Gas Productionand,Pressure Gauges In Oil & Gas Production theyll be sure to pump you up!!! Essentially, this boils down to making small changes gradually to see how they affect production. This page has been accessed 39,988 times. Today, there are two types of acceptable well tests conducted on gas wells: Well testing is typically performed by directing well production through a three-phase separator as indicated in figure 1 or if hydrocarbon liquids are too small to be measured during typical well test durations then a two-phase separator may be used. Engineers may perform formation tests to predict the likely effectiveness of treatments to remove these fines. Data that indicate how the formation reacts to pressure increases and decreases during a test can also reveal critical information about the reservoir. Gas Rate Testing (Without separator / conversion to GOR), Oil Well Testing (Gas Rate / GOR / With or without GIS), Integration with corporate initiates and production auditing, Multi-level approval of tests (can be customized to your specific needs), Compliant with regulatory measurement uncertainty requirements for Western Canada. It can also be helpful in identifying problems, but the real strength of the daily production test is showing how the behavior of a well changes over time. Some production tests are performed in open hole (such as drill stem tests) and can be used in making completion decisions. The results of these tests are very useful, and can help you find and repair problems, anticipate the lifespan of pumps and other equipment, and estimate production and plan ahead. Engineers use specific variations on well buildup and drawdown tests to evaluate gas wells.
For most tests, engineers permit a limited amount of fluid to flow from or into a formation. Even when the well is not tapping a gas drive reservoir, natural gas will usually exert some amount of pressure. They then close the well and monitor pressures while the formation equilibrates. Comparison of the final or extrapolated reservoir pressure from this second shut-in period to that from the initial shut-in period may suggest depletion has occurred during the DSTdrill stem test. Troubleshooting and diagnosing problems is going to be a big part of a pumpers duties, so its a good idea to get familiar with the equipment and how to test if its working correctly. Originally wells were tested utilizing the absolute open flow technique which was highly undesirable within the industry since there were conservation and safety risks associated. Through the implementation of theAERs Enhanced Production Audit Program (EPAP),Intricatehas identified many instances where current business processes and field procedures for periodic updates of gas production from oil wellsdoes not meet the requirementsset out by the regulator.
SHERWOOD PARK Some wells will produce more if pumps are run intermittently, which allows fluid and pressure to build up at the bottom of the well when the pump is shut in. Primarily, it will tell you whether the work over had the intended effect, solving problems or increasing production. store run tickets. This information helps analyze communication within the reservoir, tie reservoir characteristics to a geologic model and identify depleted zones.
An echometer and dynamometer are both expensive and delicate pieces of equipment, and its possible that you may not want to spring for one, or the operator you work for wont want to. The information gained from a swabbing test can also be particularly useful in determining whether a pumping unit should be installed on a well and in determining the proper pump design.
Drawing too much gas from the reservoir will lower the pressure, with the result that the wells production drops or even stops altogether. Some pumpers can get a good idea of the time required just by understanding the characteristics of the well and reservoir, and by drawing on experience. Oil was pumped out of the ground for many years before those two measuring instruments were invented, so its certainly possible to run a successfully operation without them. Engineers sometimes perform both types of tests. Safety valves allow gas to escape into the atmosphere rather than overpressure the vessel.
Finally, we go into more depth on the set-up and recording of daily tests in the GreaseBook here:The Basics Of Keeping Records For Oil & Gas Production, hereOperational Records For Oil & Gas Production Wells, and hereWell Records For Oil & Gas Production. Using optical spectroscopy, or the recorded light spectrum, engineers identify in real time the composition of fluids as they flow into the tool; this method also reveals critical data about the reservoir without waiting for laboratory tests to be completed. They can then estimate productivity gains that may be realized from a stimulation treatment. Because a surface flow rate cannot be maintained and measured, routine flow and buildup tests cannot be used to evaluate reservoir properties and determine well productivity. All rights reserved. Ideally, it should be done on the same date of each month. And, although many pumpers use a log sheet with 12 rows and enough columns to record all the results for these tests, due to the proliferation of smartphones many are switching to mobile apps like, Common Tests For Oil Well Testing and Production Allocation, The Basics Of Keeping Records For Oil & Gas Production, Operational Records For Oil & Gas Production Wells, This Week in Oil and Gas History: September 18 - September 24. Following the second shut-in period, the final hydrostatic mud pressure is measured (pfhm) and the DSTdrill stem test tool is pulled from the hole. The second shut-in period (pff2 to pfsi) is longer than the first and is used to estimate formation properties in a manner similar to that for analyzing conventional buildup tests. Wireline formation tester sampling. The gas will break out of the fluid as it is pumped to the surface. Once fluid has flowed back into the bottom of the well, the pump can be activated and the echometer used again to measure how quickly the pump draws the fluid level down. Well productivity usually diminishes over time, sometimes as a result of formation damage from fines migrationthe movement of very small particles through the formation to the wellbore where they fill pore spaces and reduce permeability. T2P 0Z3, Dawson Creek The sample may be taken from the condensate leg of a three-phase separator or the liquid leg of a two-phase separator (The water must be removed from the condensate before conducting the analysis); The GEF must be used to convert the liquid condensate volume determined during the test to a GEV, which will be added to the measured test gas volume to determine the total test gas volume if the condensate is not delivered for sale at the group measurement point (see section Directive 017 7.3.2); The WGR, CGR, and OGR (if applicable) must be determined by dividing the test water, condensate, and oil volume respectively by the total test gas volume; and, Over-sizing of gas gathering equipment (compressors, pipelines, etc. For a new well, the potential will be helpful in deciding whether the well will be profitable (meaning turning a profit while producing) and if it will pay out (meaning it will generate enough profit over the life of the well to pay for the expense of exploiting it). Using well test data, engineers predict induced or natural fracture length and conductivity. Swabbing can be defined as pulling a full-diameter tool from the wellbore; this pulling action is similar to that of a plunger in a syringe, and it initiates fluid flow into the wellbore. measure each wells productivity and performance over time, identify resources that are trapped beneath the surface, and. Factors can include the reservoirs drive, the porosity of the formation, the weight of the oil and percentage of paraffin, and the potential for scale and corrosion. The results of the test should be recorded in a record book with a separate section for each well. At its center, the packer includes a probe that is then extended into the formation to withdraw wellbore fluids.
Scientists also use downhole fluid analysis (DFA) to monitor the sampling process. A cool rod means the well is pumping properly, while a warm rod can mean there is a problem.
[3] From these data, the productivity index, PI, can be calculated as follows: The productivity index can be a useful indicator of well productivity and wellbore condition during the life of a well. When all tests are completed, the samples are brought to the surface and may be sent to laboratories for advanced testing. The problem with that oil and gas production allocation method is that the average will include any downtime for repairs or maintenance, problems downhole that may have affected production, or any other loss. That company can then manage the whole field for the maximum return and efficiency, sharing the resulting profits with the other operations. To get a full understanding of how a well is behaving, it may be necessary to run a range of oil well testing procedures and examine the results over a period of time. This production testing solution consists of accurate gas measurement equipment with current capabilities of: Since Production tests are an essential part of any operation, and the key to obtaining an indication of well productivity we suggest you be sure find a provider with accurate reporting! Pressure declines as fluid is drawn from the reservoir, eventually to the point where its no longer possible to produce oil from the reservoir. Company Bs decision to over-produce gas will have an effect on Company A and any other companies with wells in the same reservoir, possibly reducing the production potential by years. A variety of well and formation test schemes are performed throughout the stages in the life of a well or field. Other workarounds are also possible. During a backpressure test, a well is flowed against a specified backpressure until its BHP and surface pressures stabilizean indication that flow is coming from the outer reaches of the drainage area.
Production tests can also be performed when more conventional well tests (such as pressure drawdown and buildup tests) are impractical due to time constraints, well conditions, or extremely low well productivity. Then came the more practical testing methods such as isochronal testing and modified isochronal testing. This straight line is extrapolated to determine gas flow rate at a point where the flowing bottomhole pressure is zero; this rate is referred to as the absolute open flow (AOFabsolute open flow) potential of the well. The method is recommended for estimating permeability from prefracture flow test data only; it does not work well with postfracture flow data. A straight line with slope, m, should result; this slope is used in Equation 4 to calculate permeability: The apparent skin factor can also be determined from this plot. The initial flow period (pifl to pffl) is a short production period, usually only 5 to 10 min. This process is called unitizing a field. However, the more information that is available to you, the more likely you are to make a good and profitable decision. The reservoirs that are pumping wells draw from are under some amount of pressure. All from your
It will also tell you whether the work over was worth it, meaning the well will generate enough additional production to pay the cost of working it over.
Mechanical water- and oil-level controller arms, with attached floats lifted by the rising fluid, trigger valves (not shown) that release oil and water along their respective flowlines. If the well isnt new, but instead has just been worked over, potential tests are used for slightly different purposes. Operators use AOF as the basis for calculations to determine the relationship between backpressure settings and flow rates of the well. By carefully recording the volume of fluid recovered from each swabbing run as a function of time, one can determine the rate of fluid feed-in from the formation to the wellbore. We need a little more information from you before we can grant you access. In the second flow period (pif2 to pff2), the objective is to capture a large sample of formation fluid and to reduce the pressure as far into the reservoir as possible. Pumping rates vary for each drawdown, while subsequent buildups continue until the well reaches its original shut-in pressure. The four points define a straight line with a slope that is generally between 0.5 and 1.0. The objective is to release the hydrostatic mud pressure and draw down the formation pressure only slightly. Single-point tests are usually simple productivity tests that typically involve a measurement (or estimate) of initial or average reservoir pressure and a measurement of flow rate and flowing bottomhole pressure (which can be estimated from flowing surface pressure) at stabilized producing conditions. Multi-point test data can also be used to estimate permeability using a variable rate flow test analysis. The test may take a number of days, as it may take a short while after a change is made before production settles down to a consistent rate. Low permeability wells are generally broken down and balled out after completion and prior to testing; in these wells, a skin factor of 1 to 2 is often a reasonable assumption. Earlougher, R. C., Jr., 1977, Advances in Well Test Analysis: Dallas, TX, American Institute of Mining, Metallurgical and Petroleum Engineers, Society of Petroleum Engineer's Monograph 5, 264 p. Lee, W. J., 1982, Well Testing: Dallas, TX, Society of Petroleum Engineers of AIME, 159 p. Allen, T. O., and A. P. Roberts, 1978, Production Operations, Volume 1: Tulsa, OK, Oil and Gas Consultants International, 225 p. Lee, W. J., T. B. Kuo, S. A. Holditch, and D. A. McVay, 1984, Estimating formation permeability from single-point flow data: Proceedings of the 1984 SPE/DOE/GRI Unconventional Gas Recovery Symposium, Pittsburgh, PA, p. 175186. Figure 2. Single-point tests can also be used to estimate formation permeability[4] with an iterative solution of the transient radius of drainage equation (Equation 2) and the pseudosteady-state flow equation (Equation 3), as follows: To solve for permeability, an arbitrary value of permeability is assumed (0.1 md is often a good first estimate), and Equation 2 is solved for rd. By contrast, for drawdown tests, engineers open the well after a specified shut-in period to observe BHP decrease. Peace River [2] A DSTdrill stem test is run in the open hole after drilling, and is often used in deciding whether to complete a particular zone. Rather than use well tests, operators may opt to evaluate their wells using wireline formation testers that include a quartz pressure gauge and a fluid sampling tool placed across a production interval (Figure 2). And, although many pumpers use a log sheet with 12 rows and enough columns to record all the results for these tests, due to the proliferation of smartphones many are switching to mobile apps like the GreaseBook to help track these tests. In addition, capturing large fluid samples at the surface gives experts an opportunity to perform laboratory measurements on the reservoir fluids. Ideally, youll want to monitor and measure the rate at which the fluid seeps back into the bottom of the well. The single-point test method for estimating permeability is valid for constant flow rate production, constant bottomhole pressure production, or smoothly changing bottomhole pressures and flow rates. With a gravity drainage reservoir, the oil level will fall as oil is pumped out, so the perforations will need to be lowered gradually over the life of the well. The surface shut-in and flowing pressure measurements are converted to bottomhole conditions and a log-log plot of versus flow rate, q, is generated (Figure 2). Well and formation tests are also primary sources of critical data for reservoir models and are the principal means by which engineers confirm or adjust reservoir model parameters. Well tests at the exploration stage also allow operators to determine if low flow rates are affected by skin or are the result of natural permeability of the reservoir. The effects of completion choices may also be assessed using formation tests to aid engineers in planning required remedial operations. The potential production of a well is obviously a handy piece of information and youll want to note it in your well tests sheet. Or they may use a wireline formation tester to capture fluid samples and measure pressure downhole at the zone of interest. A simple formula can be used to determine how many barrels per day is produced at that flow rate. Pressure buildup tests run in other wells in the same reservoir often provide a good estimate of typical skin factors. Well testing is ultimately about the behavior of the reservoir it draws from, so it might be helpful to understand something about how reservoir pressure works. In many cases, its possible for one company to take over managing most or all of the wells in a particular area or reservoir. In addition, wireline formation testers can be used for pressure testing to determine static reservoir pressures and to confirm fluid contacts and density gradients. For example, you can take two fingers and lightly pinch the rod so that you can feel the action of the pump. Interference tests record the pressure changes in adjacent wells when the test well pressure is changed. Running a daily production test on each well can take days or weeks, and during all that time production is less than it could be. The test duration must be a minimum of 12 hours; After production begins at the proration battery, all wells must be tested within the first month, then again within six months, and thereafter annually. These data can then be used to estimate well productivity or formation permeability using the methods outlined in the discussion of single-point tests. This page was last modified on 20 January 2022, at 13:42. The barrel or bucket should be of a known volume. Don't have an account? The results of the test should be recorded in a record book with a separate section for each well. During injection tests and falloff tests, fluid is injected into the formation, and BHP, which increases as a result, is monitored. Operators may opt to obtain additional reservoir and fluid flow data by simultaneously running production logging tools into the well on wireline. 206 Pembina Road Ideally, it should be done on the same date of each month. Packers isolate the zone to be tested while downhole, or surface equipment provides well control. Red Earth Likewise, a smaller pump wont pump as fast. The well should be normalized by running it without problems or interruptions for at least 24 hours before the test.
As oil is removed, the level of water will rise, so the tubing perforations will have to be regularly raised to keep pace with the oil. This test, as you might guess, measures the ratio of gas to oil produced from the well. Well and formation tests, which entail taking measurements while flowing fluids from the reservoir, are conducted at all stages in the life of oil and gas fields, from exploration through development, production and injection. An isochronal test is a series of drawdowns and buildups. There are some productivity tests that can be performed without a great deal of special equipment.
These tests may take less than two days to evaluate a single well or months to evaluate reservoir extent. A DSTdrill stem test tool typically includes two or more clock-driven, bourdon-tube recording pressure gauges, a set of flow valves, and one or two packers. All from the field. Manning The time it takes for changes in the test well to affect pressure at the observation well gives engineers an indication of the size of the reservoir and flow communication within it.
Pistons are driven from one side of the wireline formation tester to force a packer assembly firmly against the formation to be tested.
9, 256 p. Whittaker, A. H., 1987, Mud logging, in Bradley, H. B., ed., Petroleum Engineering Handbook: Richardson, TX, Society of Petroleum Engineers. They can also derive average permeability, degree of permeability heterogeneity and anisotropy, reservoir boundary shape and distance, and initial and average reservoir pressures.
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