Currently Transneft PJSC operates over 1,400 underwater passages of main pipeline (UPMP) with a total length of about 3000 km (including flood areas). More then 150 underwater passages are constructed by directional drilling technique (DDT).
The study of the conditions for the construction of the UPMP showed that the engineering and geological conditions of drilling, technical and technological readiness of the drilling experts have a significant impact on the success and speed of the underwater crossing. One of the restrictions is also the economic feasibility of implementing directional drilling technology.
The analysis of geotechnical conditions of underwater passages construction by DDT allowed to distribute the geotechnical conditions into 5 categories. Based on the selected category it becomes possible to provide the necessary volume of geotechnical investigations for determination the requirements for drilling and rock cutting tools technology, volumes and properties of drilling mud, the time of construction.
In addition to the geotechnical conditions, the design parameters are also affected by the level of complexity of the construction of UPMP by DDT. To reduce these criteria to a single value, the constructive parameter of the underwater passage is adopted, which is the combination of the length of the underwater passage (L) and the diameter of the pipeline (D) - L*D.
Analysis of the practical results of the construction showed that the boundary of the construction of UPMP by DDT is the value of the constructive parameter L*D