The requirements to the drilling fluid weight, determined by the geomechanical modeling results, without taking into account all the factors affecting the wellbore stability, cannot guarantee accident-free well drilling in the intervals of unstable terrigenous deposits. The composition and properties of drilling fluid have a significant impact on the wellbore stability. This article has developed an approach to minimizing the problems associated with loss of wellbore stability, combining modern achievements in geomechanical modeling and physical and chemical studies of the effects of oil-based drilling fluids on core properties, which seems more effective in reducing the probability of the above problems compared to the separate use of geomechanical models and the results of physical and chemical studies. The proposed approach is based on the joint application of geomechanical modeling, hydraulic calculations and physical and chemical studies with the use of natural core from the intervals of the most unstable deposits, which allows developing a set of requirements to the composition and properties of drilling fluid to penetrate unstable rocks of a particular field. The specified set of requirements includes: requirements for weight, plastic viscosity, dynamic and static shear stresses of drilling fluid, providing mechanical stability of the borehole walls and effective cuttings transport; requirements for aqueous phase composition, the value of voltage stability of the mud, providing minimization of fracturing (according to the X-ray tomography results), softening and swelling of the rocks under consideration due to the hydration process; requirements for the fractional composition of microcolmatants corresponding to the fracture size in the rocks under consideration; requirements for the inhibiting and bridging abilities of the drilling fluid. This approach has been successfully applied when drilling a well with horizontal completion at one of the fields in the Perm Territory in the interval of unstable Carboniferous terrigenous deposits, which are prone to collapse and are penetrated at inclination angles of more than 70 degrees. The set of requirements for a hydrocarbon-based drilling fluid is established based on the results of geomechanical modeling and the above detailed studies. A drilling fluid formulation that meets the specified requirements has been developed. Engineering and technological support was carried out for the drilling of the considered well using the developed drilling fluid and monitoring of compliance with the specified requirements, which avoided problems associated with the wellbore instability.

Тенденция последних нескольких лет говорит о неизменном увеличении количества скважин с горизонтальным окончанием на территории Пермского края. Применение нескольких типов промывочных жидкостей (мультирастворная технология) в этом случае является компромиссным решением исходя из необходимости поддержания заданных проектом технологических параметров (показателей ингибирующих, реологических, триботехнических свойств) при бурении неустойчивых глинистых отложений, при вскрытии продуктивного пласта, обеспечения высокого качества крепления скважины и т.д. Практика бурения показала, что обратные эмульсии (РУО), предпочтительны для бурения скважин с зенитным углом более 70°. Прямые эмульсии (РВО) оптимальны для бурения скважин с зенитным углом до 70°. Таким образом, при строительстве наклонно-направленных скважин и скважин с горизонтальным окончанием на территории Пермского края применяют мультирастворную технологию, включающую два и более типа буровых растворов, представляющих разные типы эмульсии и последовательно меняющих друг друга в зависимости от интервала бурения. При этом требуется полная или частичная утилизация заменяемого раствора. В качестве альтернативы мультирастворной технологии разработан новый тип эмульсионных буровых растворов, способный обратимо (реверсивно) изменять тип эмульсии за счет механизмов инверсии фаз протекающей под действием комплекса ПАВ (инверторов). Данная разработка предоставляет возможность управления типом эмульсионного бурового раствора и обратимым (реверсивным) переводом его из инвертной (или прямой) эмульсии в прямую (или обратную) эмульсию без потери основных технологических свойств. Приведены технологические характеристики РИБР. На примере ОПР, прошедших на месторождениях Пермского края, показано, что при использовании РИБР можно сократить расходы на химические реагенты для приготовления и регулирования свойств бурового раствора, сократить объем сбрасываемого бурового раствора, снизить затраты на доставку химических реагентов. В ходе ОПР и дальнейшего внедрения РИБР установлено отсутствие негативного влияния на коллекторские свойства продуктивного пласта.

There are remaining recoverable reserves in the oil fields of the Perm region, which are unprofitable to develop by the traditional construction of wells (production string diameter - 168 mm) due to the high cost of building. To involve such reserves in the development it was suggested to use the construction of small diameter wells (SDW) with a changing of the traditional design in the direction of reducing the diameter of the production string. According to the results of drilling the cost is reduced up to 25 %. Despite the many advantages, the SDW design has the essential drawback - there is no reliable technology of the sidetrack drilling. That''s why some changes in the SWD structure, which allow to drill of a sidetrack with a kickoff in a technical column and, as a consequence, to save additionally of 24 % of the cost of the new SDW was suggested. Also the economic calculation was made.

The use of several types of drilling fluids is a compromise based on the need to maintain a given project of technological parameters (performance -inhibiting, rheological, tribological properties) during the drilling of unstable clay deposits, at the opening of the producing formation, to ensure a high quality of well casing, etc. This is especially true for the construction of wells with a horizontal and directional wells with zenith angle of unstable clay deposits of more than 70 degrees. A new type of emulsion drilling muds is developed, i.e. reversible invertible drilling mud (RIDM). RIDM is capable to change an emulsion type on a reciprocal (eversible) basis affected by a vatiety of chemical inverters; thus it can change its processing behavior from OBM to water-base solution and vice versa. The topic of discussion is methods and approaches used for transition oil-in-water emulsion into inverted (water-in-oil) emulsion and vise versa. Application of RIDM technical process is described. Process characteristics of RIDM are specified. Performance analysis of RIDM application in field conditions is given.

Abstract Process fluids used for operations with productive formation are considered to be a decisive reason of decreased well productivity. Application of special-purpose fluids allows eliminate the negative effect of the process fluids; these fluids don't make through a formation during operations of wells completion and workover and could be easily removed after the operations have been finished. Well- killing operation with process fluids without tunable properties is a standard well- killing technique during workover operations. Such method doesn't protect a formation from liquid penetration, and oftentimes after such workover operations it is getting rather difficult to reach the process stabilization of the well. Visco-elastic gels (VEG) act as a "flexible packer" and are designed for temporary protection of productive formation on the stages of wells’ completion and development, during workover and insulation operations. Over 350 well- killing operations by using VEG have been carried out in the territory of Perm region within 2012-2013. Application of this technique provides specified effect concerning decrease of well- killing liquid volume and saving time needed for the process stabilization. However the well pumping equipment failures have been registered due to fouling with VEG residues. Noted problems could be eliminated by applying the proposed well- killing technique by using the composition with specified destruction time. Cross-linked polymer systems gain widespread acceptance in formation fracturing operations. Provided that a considerable amount of breakers are offered at the market, they include "encapsulated" breakers designed to destruct fluids after proppant has been injected into formation. By that the induction period prior the breakers start action doesn't exceed 2-3 hours upon they have been injected into the system. For well- killing operations by VEG application it's typical to provide retention of the fluid bridging properties at least 2-3 days. In this regard conceptually new approaches are required to reach such conditions in order to control VEG "lifetime". This study presents the results of laboratory research on VEG development with controllable service life. Introduction of this technique will allow reducing the likelihood of equipment failures and accelerating the process of reaching design basis conditions of the wells.

Design was prepared and drilling technology of multilateral wells was tested on the Shagirtsko-Gozhanskoye oilfield, oilfield behalf of Arhangelskoye and Nozhovskoye oilfield in Perm region. In the process of well construction new technologies were developed and introduced.

The experience of eliminating high-intensity drilling fluids losses in fractured rocks in the Perm region fields was hight-lighted. The properties of foam cement insulating material, technology and conditions of its application were described. Results of using foam cement insulating material 6 wells are given.

Abstract A new type of emulsion drilling muds is developed, i.e. reversible invertible drilling mud (RIDM). RIDM is capable to change an emulsion type on a reciprocal (eversible) basis affected by a vatiety of chemical inverters; thus it can change its processing behavior from OBM to water–base solution and vice versa. The topic of discussion is methods and approaches used for transition oil-in-water emulsion into inverted (water-in-oil) emulsion and vise versa. Application of RIDM technical process is described. Process characteristics of RIDM are specified. Changes in emulsion microstructure during phase inversion are investigated. Performance analysis of RIDM application in field conditions is given.