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Abnormal high pore pressure forecast and geomechanical support of well construction

Object: Exploration well with AHFP. Achimov deposits. West Siberian oil and gas field. Russia.

The purpose of the work: accident-free well construction due to the forecast of AHRP zones and the prevention of geological complications

Issues: High uncertainty in the reservoir pressure profile, risks of OGVP. Lack of drilling experience for the target interval in the field.

Description of work:

A 1D geomechanical model was created with horizons marked out using VSP. The model was calibrated by reference wells. A pre-drill forecast of the pressure profile and loss gradient was made, and abnormal high pore pressure zones were determined. The risks of opening intervals incompatible with drilling during the construction of the second liner have been identified.

Recommendations were issued on the values ​​of the specific gravity of the drilling fluid for safe drilling and ECD during tripping operations. To prevent the opening of intervals incompatible with drilling, it is recommended to determine the exact depth of the second liner shoe during drilling based on an updated forecast.

At the beginning of the interval of pressure growth, geomechanical support was started:

  • Online update of the model and forecast of pressures and absorption gradient
  • Prompt issuance of recommendations on the specific gravity of the drilling mud and EDS.
  • Control of technological parameters during drilling and cementing to comply with the safe range of ECD.
  • Determining the optimal depth of the second liner shoe.

Result: all forecasts were confirmed, the well was drilled without complications.

In the implementation of this project accomplished:

Wellbore stability

Based on the obtained parameters of the geomechanical model for the planned well trajectory, the Wellbore Stability Calculation (WBS) is performed

 Overpressure forecast

Currently, near-surface hydrocarbon reserves are being depleted. The development of deeper reservoirs faces several difficulties, both technical and geological in nature. One of the reasons leading to emergency situations is the presence of abnormally high formation pressure

 Drilling risk maps

Drilling risk management map is a document that describes possible risks in the process of drilling, tripping, well casing and recommendations for their control and elimination based on geomechanical modeling

 Drilling surveillance

The goal of geomechanical support is to reduce uncertainty and prevent the occurrence of geological complications directly in the process of well construction

 Well's geomechanical modeling

1D - or borehole modeling is the base for geomechanical modeling. The 1D geomechanical model is a numerical representation of the Mechanical Earth Model (MEM) of the rock along the well trajectory. Such a model should reliably describe the behavior of the rock mass in terms of deformation and destruction
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