Integration of Different-Scale Testing Methods for Fractured Reservoir Parameters Estimation
Authors: Nikita Morozovskiy , Vadim Devyatkin , Yuriy Prokopenko 
Published: October 2016

The practice of fractured reservoir development suggests that the description of the well-bed system operation would not often conform to the behaving predicted by classical theories of filtration for fractured systems (Warren-Root et al.). It is possible, when the stratum may not be represented as a homogeneous system, and inhomogeneity dimensions significantly exceed the borehole diameter.

Under certain conditions, productivity substantiation and forecast of further work are possible, providing conventional well logging methods are used. When the survey target becomes more complicated, e.g., in the course of horizontal well logging, the solution appears to be ambiguous, thus requiring development of a new approach to interpretation.

To understand the processes during development of the reservoirs in question, computing model calculations were carried out.

Various options of vertical well locations in respect of the joint set system, as well as various combinations of configuration of the fractured reservoir entered by a horizontal well were considered.

Obtained forward solutions were compared with actual well test results and demonstrated similarity of the anomalies observed.

As the result, a set of parameters most affecting the field response was obtained, recorded during field research, which enable determination of a list of additional information necessary to complement the interpretation process.

The above surveys enabled working out and implementing of the approach of sequential interpretation of well testing and logging, based on integration of the results thereof with different-scale data (well log interpretation data, attribute seismic survey interpretation, geotechnical survey) to describe the well stream model.

The following results were obtained by implementation of the described approach:

Based on application of the proposed set of studies, a refined well stream model was obtained for analyzed deposits, specifically, for more than 15 horizontal wells, taking into account the dominating fracture influence on inflow rate;

Based on the results of the refined filtration model, the current sampling levels for wells were justified and further work forecasts taking into consideration new filtration particularities were prepared;

Recommendations of targeted geological and technological activities aimed at elimination of negative factors were issued for the wells with production performance inconsistent with the potential level.

The following conclusions may be drawn, using the obtained results:

The importance of well location (both vertical and horizontal wells) in respect of the natural macrofracture system is proven in practice;

Simulation of survey results in a computing model has proven the dominating influence of the number of fractured intervals penetrated by a horizontal well on the well stream profile, and therefore on its productivity;

Activities aimed to increase the horizontal well productivity in a fractured low-permeable reservoir shall be focused on search and involvement of the maximum quantity of natural fractures;

In case it is impossible to efficiently forecast the fracture position in the stratum, artificial initiation of such fractures is needed.

An approach to description of well performance under conditions of ineffective conventional filtration theories for fractured reservoirs has been worked out.

Based on the results of practical implementation of the worked out approach, the well stream model for horizontal wells of one of the fields in the Volga-Urals Region was justified. This enabled updating of the current production levels for wells, optimizing well operating modes, issuing recommendations of enhance production operations.