During the construction of water well drilling, the phenomenon of wellbore inclination often occurs, and a large inclination will have a serious impact on the construction. When drilling, if the well inclination is large,  it will cause increased resistance and serious wear on the drill pipe. When lifting the drill, the well deviation may cause the drill to stick, and in severe cases, it may cause a collapse of the hole and bury the drill. The well-hole inclination is the main factor causing accidents during construction, which affects the construction period, cost, and quality. What is the reason for the hole inclination?

The causes of well deviation are geological factors, drilling pressure, and equipment installation.

Geological factors

Geological factors are the objective reasons for well deviation. Generally speaking, irrigation wells are encountered in the fourth and third series of strata, which are characterized by loose upper, dense lower, uneven hard and soft, and many hard and soft layers. Soft and hard formations have different resistance to fracture, resulting in unequal drilling speeds and sloping holes. In addition, the contact surface between layers is not horizontal, and the inclination angle determines the direction of the drilling bending of the hole. Among the geological factors affecting well deviation, the main factor is the dip angle of the formation. The influence of other factors on well deviation is related to formation inclination.

The size of the drilling pressure

At present, water well drilling mainly adopts the self-weight pressure of the drill pipe, not equipped with a drilling pressure meter, the size of drilling pressure is controlled by the brake, all depending on the operator’s feelings and experience. When the drilling speed is slow, the drilling pressure is too high, and the bending of the drill pipe will easily cause the well hole to tilt.

Equipment installation

The DTH drilling rigs used in construction are mostly equipped with level gauges. Adjust the hydraulic outriggers before drilling to keep the rig level. During the drilling, the vibration of the drilling rig and the increase of the weight of rock drilling tools and drill pipes lead to the level imbalance, which may cause the well deviation if it is not adjusted in time.

There are various reasons for well deviation, and distinguishing various factors requires a combination of rich experience and theory and constant summation and refinement of solutions based on the causes of hole slope in water well construction. At the same time, choosing the appropriate operation method to avoid hole slope in water well construction will play a significant role in the construction operation.