Erosive and abrasive wear effect of water-based drilling fluid (WBM) on down-hole tools may reduce the service life of down-hole tools, and its magnetic contamination on Measurement-While-Drilling (MWD) directional tools may cause azimuth errors and reduce the wellbore position accuracy. The erosive and magnetic effects would be worse when a high density WBM densified with a high content weighting agent was employed. One of the main reasons of the erosive and magnetic effect is related to the weighting agent used. To reduce the erosive effect and magnetic interference of weighting agent, a micronized barite as a new weighting material was prepared in this paper, and then characterized by scanning electron microscope (SEM) and laser particle size analyzer.

The prepared micronized barite, as a new weighting agent of high density WBM, has great promise to reduce the drag, erosion and magnetic interference along the horizontal section of large extended-reach wells and horizontal wells. It can also be used in HTHP wells and coiled tubing drilling technology.

In our experiments, two conventionally weighting agents, barite and hematite were chosen to as the comparing samples. The erosive effects, magnetic contaminate tests, lubricity and rheological properties of high density WBM weighting with micronized barite, barite and hematite were evaluated on erosion instrument, a fluxgate magnetometer, an EP lubricity tester and a rotational viscosimeter, respectively. It was found that the high density WBM weighted with micronized barite showed less erosion, lower magnetic susceptibility, similar or better rheological properties, and smaller lubricating coefficient than that weighted with hematite or barite.

Comparing with hematite or barite, the micronized barite could effectively reduce erosive wear on down-hole tools, reduce magnetic contamination on MWD directional tools, and control the rheological property of high density WBM, which would significantly contribute to the service life of down-hole tools, the wellbore position accuracy and the safety of drilling operations.

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