Second EAGE International Science and Applications workshop Far East Hydrocarbons 2012 - From oil and gas basin studies to field models

The purpose of the paper is to provide a summary of petroleum geochemistry studies and their reservoir connectivity implications for the Chayvo field based on the samples of oil and gas collected and analyzed in the course of the field development and production beginning in 2005.

Modern technology of 3D modeling including uncertainty tools, can not only correct the existing static model, but also reduce risks in the planning and drilling of new wells. It is also important in estimation and management of reserves. As an additional tool for the distribution of petrophysical properties in between wells, Probabilistic Seismic Inversion was chosen, a recent proprietary technology developed by Shell. Probabilistic Seismic Inversion results in a 3D model tied to the log data in wells and matching to seismic in between the wells. One of the tools for evaluation of static model uncertainty was the uncertainty manager in Petrel software. The Monte Carlo algorithm was used to estimate static uncertainties.

Vertical survey uncertainty presented a challenge for the development of a thin oil column by horizontal ERD wells in the Chayvo field off the northeast coast of Sakhalin Island, Russia. A novel technique was developed to reduce uncertainty by using a well-established pressure vs depth gradient from a vertical offset well as an independent, constant vertical depth reference. Pressures were acquired in aquifers above the target reservoir and the well landing depths were adjusted to match the measured pressure gradient with the reference pressure gradient. A near-horizontal pilot hole was drilled on the first development well to establish the oil-water and gas-oil contacts and confirm the target landing depth for the subsequent production wells. This technique reduced the vertical uncertainty between wells and improved the ability to land wells as close as possible to the desire depth within the oil column.

Environmental friendly field development is a key target for Sakhalin Energy in this tough operating environment. During three years of cuttings injection in a Cuttings Re-injection (CRI) well, injection rate decreased twice, leading to two screen outs and consequent perforation of back-up zones. However domain capacity modeling indicated that injection of a bigger slurry volume should be possible contrary to reality. Using historical data records (injection pressure, volume and rate), and step rate injectivity test, an analysis was performed to understand what injection rate is a key parameter to optimize domain capacity. However the existing injection pumps (1 primary, and 1 backup) were limited to an optimal rate of 2 bpm each. Putting the two injection pumps in parallel made it possible to achieve the optimal injection rate of about 4 bpm, thereby lowering injection pressure, and making injection performance mimic domain model expectation.

The results of researches (2009-2012) of hydrocarbon resources on Russian Far East are cited. The area of prospective territory of region is 411,3 thousand km2, sea area – 702,8 thousand km2, accordingly the initial geological resources are estimated in 3 647,6 and 16 339,7 billion tons (oil value). The overwhelming part of resources is predicted in the basins of island arch margin of Pacific Ocean, where Japan Sea, Okhotsk Sea and Pripacific Ocean petroliferous provinces are outlined. Okhotsk Sea petroliferous province is the richest. Here the basic resources are concentrated in Northern Sakhalin and Western Kamchatka petroliferous regions. Structure, the degree of resource exploration, their distribution along the section and the phase composition are characterized. Also basic risks of oil and gas prospecting are determined

Models and Depositional Environments of Reservoirs of the Magadan Sedimentary Basin: a Basis of its Oil & Gas Prospects Predictions

Comprehensive approach to seismic projects in complex geological and climatic conditions, from design to interpretation