Stress‐induced borehole elongation: A comparison between the four‐arm dipmeter and the borehole televiewer in the Auburn Geothermal Well
Stress‐induced borehole elongation: A comparison between the four‐arm dipmeter and the borehole televiewer in the Auburn Geothermal Well
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DOI：
10.1029/jb090ib07p05513
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发表时间：
1985-06
影响因子：
--
通讯作者：
R. Plumb;S. Hickman
中科院分区：
文献类型：
--
作者：
R. Plumb;S. Hickman
利用位于纽约奥本的一口井的水力压裂应力测量和钻孔电视数据，研究了由四臂倾角卡尺记录的钻孔伸长的性质和起源。在地层倾角仪的两次运行中，观察到钻孔延伸的优选方位N10°W-S10°E，±10°和不太明显的E-W方位。用电视和地层倾角仪确定的钻孔几何形状的比较表明，这两种工具给出了相同的钻孔伸长方向，只要伸长区长于30 cm。地层倾角井径数据与从水力压裂试验和电视观测数据中获得的原地应力和天然裂缝方向的比较表明，N10°W-S10°E井眼伸长量（1）是轴对称的，（2）与最小水平应力Sh对齐，（3）与天然裂缝相交井无关。这些伸长被解释为应力引起的井筒破裂。E-W伸长方向的特征在于薄层岩石中的不对称钻孔横截面，并且不是由崩落引起的。这种不对称的几何形状可以通过地层倾角仪提供的定向电测量值与漏失区分开来。这项研究表明，地层倾角仪可以用来确定方向的Sh（映射突破），确认早期不太详细的研究结果，并提供了一个坚实的基础，利用现有的地层倾角仪数据映射区域应力模式。
The nature and origin of borehole elongation recorded by the four-arm dipmeter calipers is studied utilizing information obtained from hydraulic fracturing stress measurements and borehole televiewer data taken in a well located in Auburn, New York. A preferred orientation N10°W-S10°E, ±10° and a less prominant E-W orientation of borehole elongation, was observed on two runs of the dipmeter. Comparisons of borehole geometry determined using the televiewer and the dipmeter show that both tools give the same orientation of borehole elongtion provided that the zone of elongation is longer than 30 cm. Comparisons of dipmeter caliper data with orientation of in situ stress and natural fractures, obtained from hydrofracturing tests and televiewer data show that the N10°W-S10°E borehole elongations (1) are axisymmetric, (2) are aligned with the minimum horizontal stress Sh, and (3) are not associated with natural fractures intersecting the well. These elongations are interpreted as stress-induced well bore breakouts. The E-W elongation direction is characterized by an asymmetric borehole cross section in thinly bedded rocks and is not caused by breakouts. This asymmetric geometry can be discriminated from breakouts using the oriented electric measurements provided by the dipmeter. This study demonstrates that the dipmeter can be used to determine the orientation of Sh (by mapping breakouts), confirming the results of earlier less detailed studies, and provides a firm basis for mapping regional stress patterns using existing dipmeter data.