The paper presents the results of a study project of 60+ well block of the large (> 1,000 wells) mature (30 year old) oilfield in Western Siberia with objective to localise and characterize residual recoverable reserves and propose the optimal economic scenario for further depletion.

Low permeability, heterogeneous reserve structure along the cross-section, numerous induced hydraulic fractures in producing wells and numerous spontaneous fractures in injecting wells with dynamic behavior, aggravated by numerous behind-the-casing crossflows in almost every well have resulted in a very complex conditions of remaining reserves.

The conventional methods of production analysis and surveillance (well testing and production logging) do not provide a consistent picture of the current distribution and conditions of the remaining reserves and required a deeper and more complex analysis.

Development Opportunities Management workflow was chosen for this particular holistic study, which includes a set of interconnected studies, field surveillance, geological and flow modelling and culminated in field development planning based on the digital asset twin. (Ganiev, B., 2021)

Digital asset twin was constructed based on results of this workflow with a full-range economical model, flow simulation over the thoroughly calibrated fine-grid 3D dynamic model and production complication model (dynamic behavior of the fractures and behind-casing channeling).

The 3D model has been calibrated on results of the cross-well pressure-pulse surveillance, reservoiroriented production logging and was validated by the results of the drilling of the transition wells.

The digital asset twin was used to find the optimal investment scenario based on multivariate calculations with the help of digital assistants.

Due to simplicity of the user interface and client-server design, the digital twin was made available for various corporate engineers and managers without any modelling skills to play around with their own ideas on possible production/investment scenarios which gave another level of validation of the ultimate field development plan.

All activities carried out within the digital twin automatically generate a complete package of investment metrics(NPV, PI, IRR, MIRR, Cash Flow and many correlation graphs) to assessthe economic efficiency of each package and select the most appropriate solution for further ultimate choice.

The approved scenario was based around drilling 6 producing side-tracks in specific locations/trajectories, performing workovers on specific offset injectors and re-scheduling of the production/injection rates in all block wells.

The results of the field development’s activities implementation will be the subject of a future publication.

The residual reserves localization and geology specification for oil recovery increase by production enhancement operations play main role for brown fields with production decline. The set of solutions includes targeted recommendations for additional well surveys followed by workovers in production and injection wells, whole wellbore or selective stimulation, hydraulic fracturing and side tracking. As a result, previously poorly drained areas are involved in production, which increases the current rates and the final oil recovery.

The integrated technology of residual reserves localization and production increase includes:

1. Primary analysis of the production history for blocks ranking by production increase potential.
2. Bottom-hole pressures and production history advanced analysis my multi-well deconvolution for pressure maintenance system optimization and production enhancement.
3. Advanced production logging for flow profile and rate layer-by-layer allocation
4. Conducting pulse-code interference testing for average saturation estimation
5. 3D reservoir dynamic model calibration on tests findings
6. Multi-scenario development planning for the biggest NPV scenario regarding surface infrastructure

The presented integrated technology consists of several stages. The results of the first stage allow for a toplevel assessment of the current development opportunities of the area, evaluate current residual reserves (estimate displacement factor, assess conformance factor), as well as the available production increase potential for various blocks of the studied field.

Results of the second stage carried out on the block with the maximum potential allow identifying problems and offer solutions and the necessary set of studies for localization of current reserves. For the purpose an advanced logging and testing operations are used, which includes both single-well and multi-well studies.

Pulse-code interference tests, multi-well retrospective tests and reservoir-oriented production logging make it possible to scan the reservoir laterally and vertically, which is especially important for multi-layer fields.

The reservoir parameters from the test results are used to calibrate dynamic reservoir model. The effects of production enhancement operations are calculated on 3D model. The set of possible activities is evaluated in terms of their financial efficiency based on the economic model of the operator company by multiscenario approach.

The uniqueness and novelty of this approach consist of integrated usage of advanced production logging and well-testing technologies, as well as further calibration of the dynamic reservoir model on test results.

Paper presents how to apply the test results for the reservoir model calibration and increase forecast reliability by reducing the model ambiguity, how brown field profit increase.