How Does A Rotary Drilling Rig Operate in Complex Strata

When rotary drilling RIGS are working in complex strata, they need to deal with problems such as the interweaving of hard and soft strata and easy collapse. The construction strategy should be precisely adjusted in combination with the characteristics of the strata. The following introduces the specific methods from six key links.

1. Stratum prediction and scheme adaptation: Before construction, geological investigation is conducted to clarify the stratum distribution. In case of "soft on top and hard at the bottom" strata, drill first according to the soft soil parameters. When approaching the hard layer, reduce the rotational speed and increase the torque in advance to avoid equipment impact overload.

2. Strengthening of hole wall protection: Sand layers and flow-plastic formations are prone to collapse. During drilling, mud is injected simultaneously for wall protection, and the specific gravity of the mud is controlled between 1.1 and 1.3. In case of water-rich strata, casing can be used for follow-up to directly isolate the erosion of the hole wall by groundwater.

3. Dynamic adjustment of drilling parameters: In strata with alternating soft and hard layers, a "gradual" parameter adjustment is adopted. The rotational speed is gradually reduced from the soft layer to the hard layer (for example, from 60r/min to 30r/min), and the pressurization method is changed from continuous pressurization to point pressurization to reduce the risk of stuck pipe.

4. Targeted selection of special drilling tools: Toothed cylinder drills are used to break rock strata in combination with high-frequency impact to quickly penetrate the rock mass. Double-door drill buckets with diversion grooves are used in the silt layer to reduce the disturbance of mud during soil extraction. For complex strata, 2 to 3 types of drilling tools can be kept as backups and replaced in a timely manner as the strata change.

5. Wall protection and slag discharge coordination: When drilling in the sand and gravel layer, increase the viscosity of the mud (viscosity ≥20 seconds) to prevent mud leakage, and at the same time shorten the interval between lifting the drill to avoid slag deposition. The clay layer reduces the viscosity of the mud and, in combination with the rotary stirring of the drill bucket, ensures the smooth discharge of the construction waste.

6. Rapid emergency response: In case of collapse inside the hole, immediately stop drilling, add clay or rubble to backfill the stable layer, let it stand, and then re-form the hole. When the drill gets stuck, try reversing the drill bucket to unload first. Do not forcibly lift the drill to prevent the drill pipe from breaking.

The core of rotary drilling RIGS in complex stratum construction lies in "tailoring measures to the stratum" - by predicting the stratum, adapting parameters, optimizing tools and strengthening protection, it can not only avoid risks such as collapse and stuck drill, but also ensure construction efficiency and hole quality, laying a reliable foundation for subsequent projects.