Bulletin GeoHorizon

3676
 
The concept of common stratigraphic framework was previously introduced to construct and cross-validate multilayer static and dynamic petrophysical models by invoking the interactive numerical simulation of well logs both before and after invasion. This article documents the successful implementation of the common stratigraphic framework concept to examine and quantify the effects of mud-filtrate invasion on apparent resistivity, nuclear, and magnetic resonance logs acquired in the San Martin, Cashiriari, and Pagoreni gas fields in Camisea, Peru. Conventional petrophysical interpretation methods yield abnormally high estimates of water saturation in some of the reservoir units that produce gas with null water influx. Such an anomalous behavior is caused by relatively low values of deep apparent electrical resistivity and has otherwise been attributed to the presence of clay-coating grains and/or electrically conductive grain minerals coupled with fresh connate water. Concomitantly, electrical resistivity logs exhibit substantial invasion effects as evidenced by the variable separation of apparent resistivity curves (both logging-while-drilling and wireline) with multiple radial lengths of investigation. In extreme cases, apparent resistivity logs stack because of very deep invasion. We diagnose and quantify invasion effects on resistivity and nuclear logs with interactive numerical modeling before and after invasion. The assimilation of such effects in the interpretation consistently decreases previous estimates of water saturation to those of irreducible water saturation inferred from core data. We show that capillary pressure effects are responsible for the difference in separation of apparent resistivity curves in some of the reservoir units. This unique field study confirms that well logs should be corrected for mud-filtrate invasion effects before implementing arbitrary shaly sand models and parameters thereof in the calculation of connate-water saturation.

Explorer Article

3166
 
Explorer Article

Discoveries were comparatively sparse, but they persisted steadily throughout the year. Here are some of the more significant discoveries of the past year.

2058
 
Explorer Article

What’s next? Leaders of three AAPG Regions talk about anticipated activity and potential challenges their areas face in 2011. 

Explorer Emphasis

8052
 

Winning Hearts and Minds: Colombia and Latin American prospects offer high promise and difficult hurdles in the form of local political and public resistance.

2601
 

The Santos and Campos basins continue to be the world's hottest spot in deepwater and ultra-deepwater exploration.

2738
 

Latin America’s current story of exploration, development and potential may be the best known among all parts of the globe – and not just because AAPG recently held its successful international conference in Rio de Janeiro.

3302
 

A year to remember: Here’s a look at the important discoveries that made global “hit” parade in 2007.

Explorer Regions and Sections

2366
 

With expertise as both a professor and consulting geologist, AAPG President Paul Weimer’s background is well-aligned with the energy industry renaissance currently under way in Latin America.

2801
 

Colombians elected Juan Manuel Santos as their new president on June 20, the day AAPG’s presidential delegation landed in Bogotá for a whirlwind tour with both tactical and strategic importance.

750
 

As we enter the last quarter of this calendar year – one that saw the world economy shaken, global health challenged by a new flu strain and of oil and gas prices back at levels no one thought they would ever return to – we can be grateful that our Association is healthy and in good standing.

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