Page 8 - Gas Wettability of Reservoir Rock Surfaces with Porous Media

Preface

Wettability is an important component of colloid and interface chemistry, and
rock surface wettability plays an important role in petroleum engineering and
petrophysics. Rock wettability research in petroleum engineering mainly aims vii
at studying effects of water or oil phase (all liquid phases) on rock surfaces.
Rock wettability is divided into three types: oil-wet, water-wet, and mixed-wet;
whereas, effect of gas phase on rock surfaces and its influence on wettability
are neglected. Currently, there are many papers and works on researching
solid-liquid two-phase wettability, which discuss wettability’s influence on oil-
water distribution, injection efficiency, and oil and gas reservoir recovery effi-
ciency from different aspects. However, many gases with different characteris-
tics exist in oil and gas reservoirs (especially natural gas and condensate
reservoirs), which significantly impact results. Recent studies on their effect
have raised concerns among oil-gas field development. This book considers
gas phase’s existence, its effect on rock surface and influence on rock wettabil-
ity, and summarizes this significant effect and influence to a special kind of
oil and gas reservoir rock wettability, called gas wettability.

From the time gas wettability was first proposed in 2000, some scholars in
China and overseas have studied the application of gas wettability in enhanc-
ing oil recovery and water shutoff, and have obtained many important results.
However, none of the researchers or research teams systematically studied gas
wettability. There is almost negligible research on scientific implications, eval-
uation methods, reversal mechanism, and reversal materials, and there are few
studies on gas wettability’s effect on oil and gas reservoir rock properties.
Establishing wettability theory for oil and gas reservoir rock surfaces’ porous
medium is highly important for exploring and developing China’s remaining
oil and gas resources. With sustained and rapid development of China’s econ-
omy and improvement in people’s living standards, total energy consumption
has greatly increased and consumption structure has tremendously changed.
Conventional oil and gas resources can no longer sufficiently meet national
economic development requirements, and unconventional oil and gas
resources, like shale gas, etc., are gradually supplementing conventional
resources or becoming alternative energy sources. Oil and gas reservoir surface
wettability, such as gas wettability, will have a tremendous effect on oil and
gas production while exploring and developing unconventional oil and gas
resources. In order to explore economically and efficiently and develop
remaining oil and gas resources, it is necessary to establish a theoretical basis