Two fundamental advances in field development planning took place recently in the last decades. First advance is of an evolutionary type, which allows building large and detail reservoir models and is directly conditioned by the computation capacity growth. Another advance arises from a new revolutionary concept in the field development system design, called the integrated approach. Such approach means that the field development optimization should combine reservoir, well and surface facilities modeling to allow the field development managing based on maximizing technical and economic performance. The presented study describes an approach to selection of optimal strategy for the Vankor field development. Vankor is a new oil field located in poorly explored area remote from the infrastructure and services. At the time this article was prepared, there were no production wells and surface facilities. Since there are numerous alternatives to optimize field development, the special interest is paid to the field development planning. Based on the integrated digital model of the Vankor field, the commingled development of two productive zones was studied for the purpose of selecting lifting method, gathering and injection system. Introduction The goal of reservoir management is production optimization with maximum oil recovery factor under minimum costs. However, attempt of optimizing the field development system as a whole should consider for interaction of all production system elements, since optimization of one element can lead to changes in input condition and deoptimization of another elements. Moreover, using a separate simulation for reservoirs, well performance, and infrastructure, it is practically impossible to predict the system behavior if its parameters change with time (for example, changes in reservoir stimulation method, well design or surface facilities). Typically, models of wellbore and pipe flows are not constructed simultaneously with the field model construction, though the production system influences the entire field development system. Therefore, the integrated approach is required for this challenge.
One of the strategic targets in Yamal autonomous district, the Turonian siltstone formation, lies above the Cenomanian formation and is separated by a massive argillite barrier. Successful stimulation experience in vertical wells in the North-Kharampurskoe field during 2008 to 2010 encouraged the operator planning the next step of field exploration to consider horizontal well completions using multistage stimulation. The paper will describe pilot campaign in details. The Yamal Turonian formation was formed in a coastal marine environment with slow deposition rates and is composed primarily of siltstone. The major challenges of the Turonian formation are low permeability (∼0.5 md) and extremely high clay content—chlorite, kaolinite, illite, and mixed-layer illite-montmorillonite. The low temperature of the Turonian formation (below 80°F) also presents a significant challenge for gas production. An operator must produce at minimum drawdown to avoid hydrates creation. The shallow reservoir depth (∼ 3,000 ft) restricts recovering potential energy stored inside of the formation (initial reservoir pressure of about 1600 psi); therefore, hydraulic fracturing is a must for economic development of the Turonian formation. Selecting the correct fracturing fluid required extensive laboratory tests for compatibility and rheology adjustments. Thorough optimization of the fracturing fluid with clay stabilizer was applied during the course of this project. Additional challenges included proppant flowback tendency and inefficiency of conventional methods (resin-coated proppant) at such low temperatures. The project began by stimulating a vertical well that was used as a reference for the fracture horizontal well that was stimulated in three stages. Coring and a full logging suite were performed on the reference well, including acoustic measurements, post-frac, to obtain fracture height growth. It was shown that fracture is vertical at such depth and that it covers the whole interval without vertical growth into argillaceous barriers. Bottom hole gauges were used to complete the precise mechanical modeling of the stimulated reference well. Evaluation of the mechanical and properties were completed using E&P software platform-based simulator to optimize the multistage fracturing design in the horizontal well. This paper includes a detailed sequence of the operations performed and explains conclusions made concerning fracture geometry. The lessons learned during the assessment campaign are described. This stimulation project performed in the North-Kharampurskoe field is fundamental in development of the field and serves as important step toward unlocking the gas potential of other Turonian siltstones.
The end of an «easy oil times», realization of expensive projects on developing fields in the remote from infrastructure areas, with severe climate and complicated topographical conditions, raised new challenges for the field development engineering. First of all, it is related to a necessity of developing a general of field preparation prior to the detailed design and construction works.A standard approach to field development projects is based on a series of calculations on different scenarios for reservoir development, facilities construction together with economical evaluation. As practice shows, selection of optimal reservoir development scenario, irrespective of surface facilities issues, or selection of optimum surface facilities case, calculated without taking into account reservoir performance, eventually, do not provide optimal economic indicators for the entire system. Considering this interrelation, it is not possible to transfer sensitivity analysis for parameters of one system into another and, ultimately, economical indicators of the project.All this confirms that the effective, self-consistent solutions can be developed only using the integrated approach considering all aspects, affecting technological and economical field development indicators. To fulfill these objectives, Rosneft Oil Company implemented the integrated approach to field development engineering.In this article, we introduce a concept of the integrated model hierarchy, allowing classification and reservoir model construction and design process facilitation depending on problem complexity. Various models application is demonstrated on the example of one of the largest Rosneft's new fields.
TX 75083-3836 U.S.A., fax 01-972-952-9435. AbstractThis paper deals with hydraulic fracture treatment issues encountered in the Priobskoye field. The focus is the determination of fracture parameters and their variation with time.As always there are two key parameters that control the treatment effictiveness: fracture length and fracture conductivity. It is well known that, often, the actual fracture parameters are never as good as those for which the fracture is supposed to be designed for. Different reasons have been advanced in the past to explain this disparity, such as failure to fill the fracture with proppant up to the top; inefficient proppant transport into the fracture; proppant settlement by gravity; porous pack damaged with fracturing fluid gel residue. In addition, the apparent fracture paprameters may be affected by multiphase flow; non-Darcy flow; and various combinations of the above causes. Isolating the individual impact may never be possible. Despite the many approaches to describe the process of fracture design and the subsequent fluid flow in the fracture, the actual post-treatment effectiveness has not been resolved yet.The frac job analysis remains so far an urgent issue which puts a variety of challenges to the scientific community and petroleum engineers. Understanding all the phenomena that take place in the wellbore and in the reservoir during both the fracture job and the subsequent well production would allow the selection and design of appropriate fracture parameters for an economically sound field development plan.
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