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Reverse any chemical or physical changes to the formation surrounding the borehole, which was brought on by the drilling activities and or drilling fluids.

 

The second objective of well development is to improve near-well permeability and stability. By improving the permeability and stability of the area immediately adjacent to production zones, water flow into the well is maximized.

 

Improving near-well permeability and stability involves:

 

Removing the smallest size particles in the areas immediately surrounding the production zones. Whether a filter pack or open hole well is completed


The objective of improving near- well permeability and stability is the same. By removing sediment and fine particles from the near-well area, a high permeability zone is created. Thus, more water can be obtained from the well.

 

 

Often both objective one and objective two well development proceed at the same time.

 

Bentonite & Polymer Drilling Fluid additives

 

Some evidence exists that polymer drilling fluids create thinner wall cakes and break down naturally over time leaving no resistance to water flow in the near well area of the aquifer. Bentonite (clay) additives create thicker wall cakes, penetrate the aquifer and may lesson flow in the near well area unless thorough well development is done to insure the break down and removal of bentonite drilling fluid residues.

 

Bentonite additive

 

 

Polymer additive


 

 

Overview of rotary drilling fluid impact in the near well area of the aquifer:

 

Drilling damages aquifers

 

It is inevitable that some change in the permeability will occur. The impact may be slight or great, depending largely on the characteristics of the aquifer. Indeed the impact on the aquifer may even be beneficial, increasing permeability in the near well area. So too, the impact of drilling the well may be harmful in that loose grains in the near well area may be compacted decreasing permeability.

 

In “clayey” areas, the clays may be smeared over small aquifers reducing yield. The pictures above demonstrate the aquifer impact of drilling fluids introduced during the drilling process.

 

Drilling fluids have as one of their major purposes the stabilization of the borehole. However this purpose is achieved at the expense of the clogging of the aquifer. A balance must be struck between using drilling fluids to the degree necessary to permit the continued efficient making of hole and the need to quickly and efficiently remove these same drilling fluids from the water bearing formation once drilling is completed.

 

Planning for Well Development:

 


Date: 2016-03-03; view: 850


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Flushing out of the borehole drilling fluids, which were introduced during the drilling process. | The picture below beautifully illustrates the end result of a properly developed natural packed screen well.
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