| Autor: |
Kamilla Nusupbekovna Chettykbayeva, Maxim Sergeyevich Grigoriev, Alexander Anatolievich Shakunov, Stanislav Aleksandrovich Korotkov, Andrey Valer'evich Kovalevskiy, Pyotr Valer'evich Bybin, Ivan Andreevich Nikitin, Alexey Alexeevich Zinovyev |
| Rok vydání: |
2020 |
| Zdroj: |
Day 3 Wed, October 28, 2020. |
| Popis: |
Jurassic deposits of Zapadno-Yurkharovskoe oilfield include laminated sequences of sandstones and shales and characterized by overpressure (up to 830 atm at 4000m depth). The challenging clinoform geology of Achimov layers above the target formation presets the environment where pore pressure can differ significantly even in one statigraphic unit at the same depth. It is of paramount importance to determine the setting depths of production casing and that of the first liner of horizontal wells with respect to quantitative description of pore pressure increase with depth. According to the drilling history in the area, overdeepening the production section can lead to gas kick and the need of weighting up the mud, which can result in extreme losses while cementing the casing; stopping the drilling early can increase the risk of incompatible conditions in the first liner section. The objective of this study was to assess the pore pressure in real time to determine the best depth of setting the casing in the conditions of high uncertainty, since the field is not yet explored thoroughly neither by 3D seismic nor by drilling. The drilling analysis and geomechanical modeling revealed that the safe mud window of horizontal wells is extremely narrow: the drilling limits between pore pressure-collapse gradient and mud losses gradient in some intervals do not exceed 0.08-0.10 specific gravity. The established criteria for setting the production casing depth is to stop the drilling when the pore pressure reaches 1.35 g/cc of mud weight equivalent, the next section is to case the shale sequence with the increase of pore pressure from 1.35 to 2.10-2.12 g/cc of mud equivalent, lastly, the production liner cases the gas condensate bearing reservoirs drilled with the heaviest muds of up to 2.15-2.18 g/cc to offset the pore pressure and stabilize the overlying Abalak deposits, which are prone to breakout. The best drilling decisions are to made in the conditions of extremely complex geology, uneven pore pressure distribution and in the absence of seismic inversion results. The established criteria for well design and the techniques of pore pressure assessment have already proved positive for the well #5. These experience and methodologies can be interesting and useful for other projects managing the overpressured low permeability reservoirs in Western Siberia as well. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
|
