Shut-in period

It is common practice to record the bottom hole pressure firstly during a flowing period (pressure drawdown test), and then during a shut-in period (pressure build-up test). During the flowing period, the FBHP is drawn down from the initial pressure, and when the well is subsequently shut in, the bottom hole pressure builds up. 

In high permeability reservoirs, wells may produce dry oil for a limited time following a shut-in period, during which gravity forces have segregated oil and water near the wellbore. In fields with more production potential than production capacity, wells can be alternately produced and shut in (intermittentproduction) to reduce the field water cut. This may still be an attractive option at reduced rates very late in field life, if redundant facilities can be decommissioned to reduce operating costs. 

Quaternary ammonium salt polymers are more versatile and have been used in drilling fluids, completion fluids, acidizing treatments, and hydraulic fracturing. No well shut-in period is required. 

Smaller modules would allow for greater flexibility in handling production buildup and declining volumes during field depletion. They would also reduce the curtailment of production during shut-in periods for major repairs, turnarounds, or possible plant disasters. 

Gas hydrates formed during a restart after the platform was shut down due to a hurricane. During the shut-in period the gas dehydrator partially filled with water. After production restarted, since the dehydrator was not cleaned properly, it was not dehydrating gas as designed and wet gas entered the export line, causing... 

At Grass Creek (Fig. 4c), the calcium concentration peaked considerably later than at Crooks Gap (Fig. 4a)—about 3 months after the well was put back on production. At Grass Creek, high cation concentrations 3 months after production are an indication that the area of the reservoir affected by the CO2 was some distance away from the treated well. The water composition profile and the fact that the well produced very little incremental oil is an indication that the CO2 bypassed the area around the well bore and went directly into the water leg, where it resided during the shut-in period. This is illustrated by the schematic scenario in Fig. 14, showing how updip waterflood injectors helped push the CO2 downdip into the water leg, which was only 14 m (46 ft) laterally and 3 m (9 ft)... 

Siddiqui, M. A., Nasr-El-Din, H. A., Al-Anazi, M. S., and Bartko, K. M. Formation Damage in Gas Sandstone Formations by High-temperature Borate Gels Due to Long Term Shut-in Periods, SPE/DOE Symposium on Improved Oil Recovery, April 17-21, 2004, Tulsa, Oklahoma (SPE 89476). 

Pump-Back Tests. Well 40. An important aspect of the field evaluation was to determine whether undegraded polymer could be recovered from the injection well after a 2-week shut-in period. After injection of 3,000 bbl [447 m ] of polymer in FMB containing 1.1 ppm active Biocide K, 25 ppm citric acid, and 900 disintegrations per minute per gram (dpm/g) of tritiated water into Well 40, the first pump-back test was conducted. After the 2-week shut-in period, a rod pump was installed in the injection well so that fluid samples could be recovered. A total of 400 bbl [64 m J of polymer... 

Unfortunately, the pump-back test after the well shut-in period showed severe polymer loss (Fig. 17). The cause of the low viscosities in the pump-back samples was attributed primarily to bacterial degradation of the polymer. This conclusion was supported by the high levels of bacteria (10 to 10 bacteria/cm ) in the produced samples. Polymer adsorption on the reservoir rock was not a likely cause of the polymer loss because 230,600 bbl [36.66 x 10 m ] of polymer solution had passed through the fracture, and all adsorption sites should have been satisfied. Iron levels were still high (25 to 100 ppm) despite use of a stainless steel rod pump and... 

To evaluate the effectiveness of H2S as a biocide in the Tensleep reservoir, 11,200 bbl [1.78X 10 m3] of polymer solution was injected into Well 74. Measurable but not serious plugging was observed on the fracture face. Every precaution was taken to eliminate oxygen from the injection plant facilities (oxygen levels just upstream of the wellhead were always < 10 ppb). Because tritium was used as a tracer in the second test, cobalt-57 was used as the tracer in this test. After the 2-week well shut-in period, polymer levels in the produced fluids were only about one-half of what was expected from the tracer results (Fig. 18). All of the available evidence led to the conclusion that the H2S in FIB did not prevent bacterial degradation of the polymer. This conclusion was supported by the fact that high levels of aerobic, general facultative-aerobic, and sulfate-reducing bacteria were found in the produced solutions. It was not apparent why bacterial control was successful in the laboratory and not in the field. 

Bacterial control in polysaccharide polymer solutions appeared attainable according to laboratory results but could not be sustained in the field. Three single-well pump-back tests showed very severe near-wellbore polymer degradation after a 2-week shut-in period. 

A shut-in period may be unavoidable, as a result of logistics and the time it takes to repipe lines and turn a well around. Sometimes a well does not produce back immediately, and assistance, such as swabbing and jetting with nitrogen, is required. Hopefully, the shut-in period can be limited to two to eight hours. Beyond that range, there is cause for concern, especially with lower-permeability sandstone formations with complex mineralogy, which are conducive to spent-acid reprecipitation reactions. 

HF shut-in time should be minimized to reduce repredpitation of reaction products. One should be skeptical ofHF treatments thatreqube an intentional shut-in period as part of the procedure, even in high-permeability formations. If HF shut-in is to exceed one day, the overflush should be designed to displace spent HF three to five feet from the wellbore. 

Unnecessary shut-in time can lead to reprecipitation of acid reaction products near enough to the wellbore to cause radial permeability damage. This is espedally true in cases in which acid was not or could not be displaced far away from the wellbore. Generally, intentional shut-in periods in sandstone acidizing treatments are questionable. 

The properties of the neat inhibitor formulation (i.e. as received from the formulators) are important mainly from the standpoint of handling the material. Low viscosity is necessary to provide adequate pumping rates or flow rates. For example, when an oil well is treated batchwise, the time to reach the bottom and the hang-up on the surfaces depends on viscosity, which accordingly affects the shut-in period. Downtime costs money. 

In any case it has to be taken into account, that the paper mills have to reduce their shut down periods to an absolute minimum because of the economical pressure coming from the globalisation of the industry. 

Beside all these safety reasons, we are able to test 2 or 3 drums at the same time and by some improvements of the application we are able to reduce the test-period down to 4 hours, which results in an also for the production sufficient number of tested drums during the short shut down periods. These increase the availability and the production output of a plant and result therefore in a gain of safety an economical competitiveness of the European industry. 

The only meaningful solution is a pneumatic test in conjunction with an AE. Beside the high sensitivity of an AE and its reliability in combination with an established and proven data base, the method can be performed by experienced testing agencies easily and within short shut down period. A lot of 4 up to 9 drums can be tested within one day. 

Another method of using CO2 is called cycHc CO2 stimulation or huff n puff (26). A limited amount of CO2 is iajected into a reservoir over hours or days. The well is then shut in for a soak period of days to weeks to allow the CO2 to interact with the cmde oil, swelling the oil and reducing its viscosity. 

The normal regeneration temperature in the still will not regenerate heat-stable salts or oxazolidone-2. Therefore, a reclaimer is usually included to remove these contaminants. A side stream of from 1 to 3% of the MEA circulation is drawn from the bottom of the stripping column, This stream is then heated to boil the water and MEA overhead while the heat-stable salts and oxazolidone-2 are retained in the reclaimer. The reclaimer is periodically shut in and the collected contaminants are cleaned out and removed from the system. However, any MEA bonded to them is also lost. 

Quicklime is less easy to handle, and swells considerably on hydration. It is cheap, however, and is often used on open trays to protect process equipment, machinery, furnaces, etc. during shut-down periods. If it is accidentally flooded with water, the slurry of hydrated lime provides an alkaline medium in which uncoated steel surfaces will remain without rusting. 

Sometimes it may become necessary to shut-in a gas well when the demand for gas is low. In such instances, the well is shut-in for an indefinite period, after which it is reopened and production is resumed. It often has been found that the production rate of gas from the reopened well is substantially less than it was before the well was shut-in. During production, the inner wall of the production tubing will be coated with a film of condensed freshwater because of the geothermal gradient. This water flows down when production is interrupted and can cause formation damage. This may occur because clays are normally saturated with brine water and not with freshwater. This swelling can be prevented with the injection of some additive, for example, sodium chloride, potassium chloride, calcium chloride, or an alcohol or a similar organic material [1853]. 

The problems in fixed bed cracking reactors are (1) heat must be supplied to heat the reactants to the desired temperature and overcome the endothermicities of the cracking reactions and (2) the reactor must be shut down periodically for coke removal. Both of these problems were overcome by the development in the 1940s and 1950s of a fluidized... 

Inputs = Outputs + Sinks + Accumulations The sink term of a material balance is Vrra and the accumulation term is the time derivative of the content of reactant in the vessel, or d(VrCa)/dt, where both Vr and Ca depend on time. An unsteady condition in the sense used in this section always has an accumulation term. This sense of unsteadiness excludes the batch reactor where the conditions do change with time but are taken account of by the sink term. Startup and shut down periods of batch reactors, however, are classified as unsteady. 

An alternative that is less resource-intensive than the flow loop is the flow wheel apparatus (Bakkeng and Fredriksen, 1994 Lippmann et al., 1994) shown in Figure 6.4b. The wheel (torus) is nominally a 2-5 in. (5.1-12.7 cm) pipe, 2 m in diameter that rotates at 0.3-5.0 m/s while filled with gas and less than 50 vol% liquid. Conceptually, the wheel is spun past the gas and liquid rather than the reverse. Therefore, the flow wheel apparatus does not require circulating devices such as pumps or compressors. Hydrate formation is deduced visually, or by a sharp increase in torque required to turn the wheel. Urdahl et al. (1995) and Lund et al. (1996) report good field transferability from results obtained with this apparatus. Pilot flow loops and flow wheels have been also used to simulate shut-in/start-up conditions (12 h stagnant period) and to test kinetic inhibitors (e.g., Palermo and Goodwin, 2000 Rasch et al., 2002). 

After spending weeks performing an intensive investigation, technical services finds that the equipment manual for the piece of equipment (which was still with the vendor) has a disclaimer that plainly states that the equipment must undergo a 3-month break-in period during which the rate of production is 60-80% of the final production rate. Further, this manual also states that the equipment must be lubricated once an hr for the first month. If not lubricated, the equipment will shut down. 

Carefully review startup and shutdown procedures and the consequence of a time delay in any step of the process. Evaluate the consequences of an extended hold or shut down period on plant operation. 

Zffs, Number of prod, lines shut down at plant f at site s in period t... 

In all the zones in both the buildings, it is seen that the build-up of TVOC levels during system shut-down periods are quite low and the introduction of ventilation is often able to dilute the TVOC levels to a reasonably acceptable level. 

In steady state operation, both reactors tested performed equally well, but the fully packed reactor was found to be superior in handling shut-down periods. The methane production was found to be 0.347 liter (STP) per gram of COD destroyed. 

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