Sakhalin Energy

In the face of cumulative effects of oil and gas activities on the endangered western gray whale, informed management decisions rely on knowledge of gray whale spatial use patterns as a function of demographic group and prey energy. In particular, the gray whale foraging ground off Sakhalin Island consists of two distinct areas (nearshore and offshore) with the offshore feeding area exhibiting markedly high prey energy content. Based on photo-identification data collected from 2002 to 2015, we determined that gray whale use of the offshore feeding area increased with age. Pregnant females were more likely to be sighted only nearshore when nearshore prey energy and the proportion of nearshore energy from amphipods were higher. Likewise, females arriving with calves were less likely to be sighted offshore when the proportion of nearshore energy from amphipods was higher. Photo-identification effort in 2015 was increased substantially, with the intent of maximizing resighting data of individual whales to determine the relative proportion of different demographic groups utilizing the nearshore and offshore feeding areas. Comparing sighting data collected in 2015 with data from all previous years combined, mothers arriving with calves were sighted in the offshore feeding area earlier in 2015, with no evidence that they returned to forage nearshore later in the season. Other reproductive females constituted a higher proportion of the animals foraging nearshore prior to 2015, while juveniles were a higher proportion during 2015. Thus, the offshore feeding area is an important component of the gray whales' annual life cycle, particularly if nearshore prey energy continues to decline, and offshore anthropogenic activities need to be monitored and addressed.

Based on satellite images in the visible range, the boundaries of ice zones of various ages in the Sea of Okhotsk and the Tatar Strait for mid-February and mid-March in the period from 2000 to 2020 were delineated. Zone's areas were calculated using microwave range satellite imagery considering ice concentration. Average ice thickness was calculated based on the hummocking coefficient of ice extent. Based on these data, ice volume at the phase of maximum development of ice extent in the studied water areas was calculated using the "ICE " software package as average value for February and March. From the analysis of inter-seasonal variations, it was concluded that for the studied period the volume of ice in the Sea of Okhotsk decreased by-56%, or 292 km3. The average rate of ice decrease in the Sea of Okhotsk was-27%/10 years, in region I-18%/10 years, in region II-34%/10 years and in region III-29%/10 years. The ice volume change was-42% due to decrease in ice cover and-58% due to decrease in ice thickness. In the Tatar Strait, the volume of ice decreased by-30% (-3.4 km(3)). Since the ice cover of the strait remained constant during the period under study, the ice volume declined solely due to decrease of the ice thickness.

The article describes the practical application of developing project management methods. For the management of large-scale projects, an integrated approach to monitoring and control is proposed based on the preliminary division of a large-scale project into phases and the combined use of technologies of Earned Value Management and Earned Duration Management. With this approach, it is convenient to coordinate the participants—stakeholders involved in the implementation of individual phases—and to take into account risks and uncertainties during the period of forced shutdowns of existing production in order to ensure the integration of newly built facilities with existing ones. Modified indicators for Earned Value Management and Earned Duration Management for project phases are introduced.

Based on the interpretation and analysis of data obtained from passive and active microwave spectroradiometers installed on artificial Earth satellites, the boundaries of the ice extent zones in the Sea of Okhotsk with different age characteristics for the period from 2000 to 2020 have been defined and discretized into monthly components. Weighted average ice thickness in the selected zones has been calculated for three dominant age groups of ice according to World Meteorological Agency Nomenclature without adjustment for ice deformation. Analysis of the estimated characteristics has allowed us to conclude that in the XXI century there was a decrease in the volume of ice in the Sea of Okhotsk by 162 cub.km (or 51.9%). Ice volume decreased at average speed of 7.7 cub.km (or 24.7%) per decade, while ice extent decreased by 11.2% per decade (or 23.6%), and weighted average ice thickness – by 14.1% per decade (or 29.6%). For the 2000 to 2020 research period, changes in the volume of ice have been due to decrease in its thickness by ~ 56% and ice cover by ~ 44%. It has been established that the nature of the development of the ice regime parameters within the boundaries of the regions of the first hierarchical level varies significantly.

The cuttings re-injection (CRI) well in the Astokh area of Piltun-Astokhskoye field offshore Sakhalin Russia is one of the longest operating drilling waste disposal wells in the oil and gas industry worldwide. The Astokh area has been developed as a waterflood and is operated by Sakhalin Energy, a joint venture between Gazprom, Shell, Mitsui, and Mitsubishi. The Astokh CRI well has been utilized for waste injection for over 16 years. About 300,000 m3 of waste has been disposed into the main injection zone of the CRI well. Monitoring and modelling the CRI process to understand the evolution of the disposal domain is paramount for safeguarding further disposal operations. The disposal domain can be described as a complex system of multiple hydraulic and natural fractures due to injection under fracturing conditions. CRI domain evaluation includes analysis of historical injection pressures to identify the reasons of continuous injection pressure increase with increasing cumulative waste volumes disposed, to confirm domain containment, and to predict remaining domain capacity. Transient pressure analysis has revealed that the fracture closure pressure, driven by pore pressure increase and the accumulation of injected solid-phase waste, is the key parameter affecting injection pressures. Injection intensity, periods of shut-in, large overflushes, and solids-free liquids injections with corresponding solids and stresses redistribution are the other factors that affecting the pressure trends. CRI domain mapping was carried out with history-matched time-lapse 3D hydraulic fracture models. Injection pressure history matching results reveal the fracture geometry evolution during well life. The distribution of the injected liquid phase in the sand layers was modeled with a 3D dynamic reservoir sector model, matched with injection pressures and with formation pressure data in two offset wells, located at a distance of 1 and 2 kilometers, respectively. A matched model was then used to assure fracture containment for future waste disposal and to estimate remaining domain capacity. High-precision temperature and spectral noise logs were acquired in seawater injection and shut-in modes. The log-derived fracture height confirmed the domain size predicted by the matched model. 4D seismic data processing revealed that dimensions of Geomechanically Altered Rock Volume (GARV) were also in the same range as predicted by the model p. The integration of CRI domain evaluation with matched 3D hydraulic fracture models, well logs and 4D seismic demonstrated that injection pressure data collected during every injection cycle may be sufficient to characterize disposal domain evolution and to estimate domain capacity.