Injection well construction

Reinjection wells are usually constructed of either 2-, 4-, or 6-in. PVC. The screen portion of the well usually has slotted openings. Oversized screen openings and 

FIGURE 8.6 Photographs showing microbial activity and scale buildup on injection well screen (a) and within casing (b). 

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A detailed discussion of the technical aspects of industrial-waste injection-well construction can be found in Warner and Lehr.6 U.S. EPA20 also presents a survey of well construction methods and materials used for 229 hazardous waste injection wells. Two types of injection well completions are used with hazardous waste injection wells ... 

Reverse circulation U or C 2000+ M,R,I plugging of certain formations is critical good for recovery and injection well construction continuous coring available produced fluids require handling (hazardous if NAPL is encountered) Formation relatively undisturbed compared with other methods large-diameter boreholes can be drilled ... 

Examination of the records of wastewater injection wells that have been constructed in the United States shows that almost all the wells constructed thus far have been completed by one of three methods or close variations of them. The methods are ... 

Most wastewater injection wells will be constructed with injection... 

Most injection wells are drilled using the rotary method, although, depending on the availability of equipment and other site-specific factors, reverse-rotary or cable-tool drilling may be used. The construction of an injection well incorporates several important elements28 ... 

The injection of produced water and other oil held fluids into wells started as early as 1928. In 1976, more than 300 industrial waste disposal sites were in operation throughout the country. By 1986, approximately 60 million barrels of oil held fluids were injected through 166,000 injection wells within the conterminous United States. These volumes are anticipated to increase significantly in the future as producing helds continue to be depleted. Thus, construction requirements as listed in 40 CFR 146.22 are an essential prerequisite to the safe disposal/injechon of fluids and the prevention of contamination of USDW. 

Drilling Techniques for the Construction and Installation of Monitoring, Recovery, and Injection Wells... 

Floating product migrates toward the well at a rate proportionate to the hydraulic gradient. As production wells deplete oil reserves in the immediate vicinity, the oil must travel farther, over lesser gradients, to reach the well. The end result is reduced oil production. Construction of new wells at more advantageous intermediate locations will revitalize production. An alternative procedure is to install an injection well between recovery wells. The increase in the hydraulic gradient caused by the injection well would then stimulate oil flow toward the recovery wells. 

Mountain Arsenal Deep Injection Well was constructed in 1961, and was over 12,000 feet deep. Over a four-year period, 165 million gallons of waste were pumped into the well. Records indicate that pumping took longer than anticipated, because of the impermeability of the rock. (Thus, it may be assumed that pumping pressures were very high.) In 1966, use of the well was discontinued because of the possibility that the fluid injection was triggering earthquakes in the area . Details can be found in Reference [8]. 

Since equation 39 is linear, superposition of component solutions is permitted. It becomes straightforward to construct solutions for a finite domain reservoir for multiple production and injection wells as long as they are far away from each other for pressure buildup, that is, turning off a production well and for pressure drawdown. 

The bottomhole pressure of injection wells was determined according to the known barometric formula. However, for the gas wells a correction was made for the increase in gas density. The steam density was calculated to be 20-30% higher on account of the moisture content, and gas density was assumed to equal 0.7 of air density. Inasmuch as the pressure changes in the production-observation wells were not significant, the effects that the injection wells exerted mutually among themselves could be ignored. In other words, it was assumed that all injection wells operated independently of one another. Before the pressure field map was constructed, all pressures measured in the production-observation wells were brought up to the moment at which steam injection was discontinued. Visual extrapolation was used for that puipose. 

Pressure increases in the production wells were not uniform. For this reason, the lack of uniformity in parameters of filtration along the lines injection well-production well had to be taken into account when constructing the maps of pressure fields. An isobar map showing the stationary field of injection is given on Rg. 45. 

Fig. 65. Bottomhole construction of injection wells used for bed ignition with process of in situ combustion.

The USEPA currently groups underground injection wells into five classes for regulatory control purposes and has a sixth class under consideration. Each class includes wells with similar functions, construction, and operating features so technical requirements can be applied consistently to the class. 

Permeable treatment beds Deep well system Extraction/injection well system Extract wells/seepage basin Excavation, transport and disposal Hydraulic dredging Mechanical dredging Drum handling Slurry wall construction... 

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