Valery Vasilievich Shako

Modeling of Rock Permeability Damage and Repairing Dynamics Due to Invasion and Removal of Particulate from Drilling Fluids

The investigation discussed in this paper was motivated by the need for model which is able to simulate both permeability reduction of hydrocarbon formations due to the mud-component invasion during over-balance drilling, casing/cementing, workover operations, and dynamics of permeability repairing during well cleanup. The paper focuses on development and validation of model to describe internal mud cake (IMC) dynamics, placing special emphasis on dynamics of the IMC removing during well cleanup procedure. Set of laboratory experiments with clay slurry injection and subsequent brine water backflow in samples of Bentheimer sandstone is discussed. The specific of these experiments is that backflow was carried out with alternating rates (“multirate” backflow). It is shown that the conventional deep-bed filtration model is not able to reproduce the dynamics of multirate backflow. The stochastic model we suggest takes into account pore size distribution and describes the mobilization of trapped particles within individual groups of pores within a “pore ensemble.” We provide simulation results to show that the suggested model reasonably reproduces permeability dynamics during both clay slurry injection and brine water backflow stages.

Temperature Monitoring Results for Methane-hydrate Sediments in the Nankai Trough, Japan

The Japan Oil, Gas and Metals National Corporation (JOGMEC) conducted the Kisoshisui (Tokaioki-Kumanonada) drilling campaign in the Nankai Trough area during 2003–2004 as part of the activities of the MH21 Research Consortium, which is supported by the Ministry of Economy, Trade and Industry (METI). Through this campaign, various subsea hydrate studies were conducted using various data, including logging while drilling, wireline, coring, and temperature measurement. Using recent technology, a precise in-situ temperature measurement system was successfully developed and deployed at the beginning of the drilling campaign. The goals of the study were to determine whether the measurement system and setup can reliably measure the equilibrium in-situ formation temperature, to determine if the measurements adequately delineate the geothermal gradient, and to identify any disturbances in the thermal regime of the hydrate-bearing sediment and the possible causes of the disturbances. The temperature of the hydrate-bearing sediment was monitored in a deep-water well for 1.5 months. Because the measurements were collected over a long period of time, the equilibrated formation temperatures could be readily determined after observing the thermal relaxation from drilling and sensor deployment effects. The temperature profile and the temperature gradient through the hydrate-bearing zone were estimated in a quasi–steady-state condition. A correlation between the tidal cycle and sea-floor temperature change is also discussed.