Hard-to-recover reserves comprise about 70 percent of Gazprom Neft’s project portfolio. These include residual deposits in depleted fields, and low-concentration and low-porosity reservoirs, that can only be developed using high-tech horizontal and multilateral wells —which Gazprom Neft is building using cutting-edge downhole equipment, remote online monitoring technology, and organisational technologies directed at optimising the drilling process and reducing costs.
Rotary drilling systems (RDS)
Building high-tech wells demands a range of specialist equipment. The basis for modern, effective, precise and safe drilling these days lies in rotary drilling systems (RDS).
RDS make it possible to drill both perfect-deflection-angle wells, with along-hole displacement of less than 0.2°, as well as horizontal wells running to a length of more than 2,000 metres.
Using RDS makes it possible to build extreme-reach wells, and to conduct high-precision well drilling in low-concentration reservoirs (one to two metres thick).
Until recently, fields in Russia developed using RDS would use internationally-produced systems. Over the past few years, however, Russian-produced RDS, developed by St Petersburg’s CSRI Electropribor and Burintekh, have been successfully tested at Gazprom Neft fields.
The Gazprom Neft Drilling Support Centre (DSC) was established specifically to improve efficiency in building high-technology wells. The DDC supports the construction of practically all complex facilities, including high-load wells, wells with extended horizontal sections, and ultra-deep and multilateral wells. In addition to this, the Centre monitors the drilling of all wells designed for developing hard-to-recover hydrocarbon reserves, and supports the pilot testing of all new drilling technologies.
The DSC’s work is predominantly based around geo-steering technology, which involves obtaining information on a field’s geological model, in real time, with adjustments made to the well trajectory in line with this. Data is transferred from the boring (drilling) tool to the DSC in real time, and updated information displayed on the geological model of the field. Actual data is compared against projected data, analysed, and, if necessary, the well trajectory corrected on that basis in order to fall within the target zone. Then, as new data is received, the cycle is repeated, allowing uninterrupted control over drilling operations.
A serious problem, that reduces accuracy in drilling a well into an oil reservoir has, until recently, been delays in receiving data on surrounding rock through drilling tools — the design of which does not allow sensors to be placed within 15 metres of the drill-bit. To solve this problem the Gazprom Neft Science and Technology Centre has developed the industry’s first self-learning programme for optimising costs in drilling complex wells, making it possible — on the basis of inferential data — to clarify strata geology and, where necessary, take a decision on correcting the drilling trajectory, in real time.
This programme analyses metrics (such as the level of vibration, drilling speed, rotor spinning and drill-bit pressure) that change in line with the nature of the strata, making it possible to determine rock composition quickly, without having to wait for data from sensors to reach drilling equipment itself.
This programme is self-learning while in use, so predictions as to the surrounding rock become more precise with every metre drilled. Accuracy in predicting changes to surrounding geology during well drilling in commercial tests at Gazpromneft-Yamal assets has reached 70 percent.
The “Technical Limit” in drilling
Technological advancement isn’t just about using cutting-edge equipment and undertaking uniquely complex operations. It’s also about the right production culture, allowing operations to run at maximum efficiency.
In order to achieve the best possible outcomes at the lowest cost, Gazprom Neft is deploying its “Technical Limit” programme throughout its drilling operations. The idea behind this approach lies in identifying the limits to efficiency improvements, and scope for optimisation, benchmarked against the standard well-drilling process.
The full project can be divided into several components: high-quality planning; selecting optimal technologies; completing planned operations and works; and analysing results and lessons to be learned in order for these to be taken into account in the next work-cycle.
Implementing the Technical Limit programme has facilitated a significant reduction in well-construction cycles, reduced capital costs, and improved workplace safety. A further step forward in improving drilling efficiency has been the deployment of the “Optimised Well Design” project — the point behind this lying in combining technologies selected in line with each individual field’s specific geological conditions. Key elements in these optimised selections include — changing well design, from three-column to two-column structures; choosing new drilling regimes and completion technologies; and using hydrocarbon-based drilling fluids, and recycling these (“recovery and reuse”).
“Optimised Design” was used for the first time by Slavneft-Megionneftegaz in 2017, proving highly effective and cutting drilling time by 59%. In 2018, while drilling a well in the deepest strata at the Slavneft-Megionneftegaz Vatinskoye field, the time taken in drilling two horizontal wells was cut from 56 days using standard technology to 25.96 days using “Optimised Design” methodology.