Work objective and subject

The main work objective is optimization of field development and well operations by providing recommendations on selection of optimal intervals for horizontal well placement and safe drawdown pressure limits in PK1 gas reservoir for minimizing risks of sand production.

Up to 25% of the gas from the total recoverable reserves of gas assess of PJSC "NK "Ronseft" in the territory of Russian Federation is concentrated in PK1 formation, which makes it attractive for commercial field development. The uniqueness of the object is determined by the type of reservoir: highly porous and highly permeable weakly consolidated sandstone, which imposes a number of limitations on completion design and operating parameters.

Used methods, technologies, process description

A significant volume of special studies has been carried out to enhance quality and credibility of geomechanical modeling results: broadband acoustic cross-dipole logging, formation micro-imagers, extended leak off tests, pressure tests and fluid sampling, coring for complex petrophysical and geomechanical lab experiments.

Based on the obtained information 1D geomechanical models were calculated for several offset and reference wells and calibrated on drilling results of first horizontal wells in PK1 reservoir of the Kharampur field. According to the results of 1D geomechanical modeling, calculations of safe and critical drawdown pressure are made for sand potential prediction during production. Specialized core samples tests are planned and conducted (thick-wall core cylinder tests) to calibrate modeling results.

Results and conclusions

Based on geomechanical model and the results of thick-wall core cylinder test, the values of safe and critical drawdown pressure along the wellbore were determined for initial reservoir conditions.

It's defined that the planned interval of horizontal well placement in some parts of the study area is characterized by lower value of safe drawdown pressure (DD<2.5 atm.) than was planned in the preliminary field develompent strategy. To achieve the planned volumes of cumulative production, it is proposed to review the placement of horizontal wells in intervals and zones where the critical drawdown pressure corresponds with or may be higher than planned one.

Novelty of work and achievements

As part of project implementation, at the planning stage of the field development strategy an expanded set of advanced logging and measurements was carried out on a number of offset and reference wells to increase the reliability of the petrophysical and geomechanical models.

To confirm the results of drawdown pressure limits calculation on the basis of geomechanical parameters a new method developed and special lab experiments (thick-wall core cylinder tests) were conducted for predicting several states of the rock during loading-deformation process and estimate safe and critical drawdown pressure.

The results of geomechanical modeling are used as a basis for project design documentation and will be used to calculate the optimal parameters of well operation and increase the efficiency of field development.

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