<?xml version="1.0" encoding="ISO-8859-1"?><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<front>
<journal-meta>
<journal-id>0016-7169</journal-id>
<journal-title><![CDATA[Geofísica internacional]]></journal-title>
<abbrev-journal-title><![CDATA[Geofís. Intl]]></abbrev-journal-title>
<issn>0016-7169</issn>
<publisher>
<publisher-name><![CDATA[Universidad Nacional Autónoma de México, Instituto de Geofísica]]></publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id>S0016-71692018000200151</article-id>
<title-group>
<article-title xml:lang="en"><![CDATA[Amplitude versus offset (AVO) modelling and analysis for quantitative interpretation of porosity and saturation: A case study for Sawan gas field, middle Indus basin, Pakistan]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Rizwan]]></surname>
<given-names><![CDATA[Muhammad]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
<xref ref-type="aff" rid="Aaf"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Akhter]]></surname>
<given-names><![CDATA[Gulraiz]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Mustafa]]></surname>
<given-names><![CDATA[Ali]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Bin Nisar]]></surname>
<given-names><![CDATA[Umair]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Ashfaq]]></surname>
<given-names><![CDATA[Khawar]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
</contrib-group>
<aff id="Af1">
<institution><![CDATA[,Quaid-i-Azam University Department of Earth Sciences ]]></institution>
<addr-line><![CDATA[Islamabad ]]></addr-line>
<country>Pakistan</country>
</aff>
<aff id="Af2">
<institution><![CDATA[,COMSATS Institute of Information Technology Department of Meteorology ]]></institution>
<addr-line><![CDATA[Islamabad ]]></addr-line>
<country>Pakistan</country>
</aff>
<aff id="Af3">
<institution><![CDATA[,Quaid-i-Azam University Department of Earth Sciences ]]></institution>
<addr-line><![CDATA[Islamabad ]]></addr-line>
<country>Pakistan</country>
</aff>
<aff id="Af4">
<institution><![CDATA[,Petroleum Exploration Private Limited  ]]></institution>
<addr-line><![CDATA[Islamabad ]]></addr-line>
<country>Pakistan</country>
</aff>
<aff id="Af5">
<institution><![CDATA[,COMSATS Institute of Information Technology Department of Earth Sciences ]]></institution>
<addr-line><![CDATA[Abbottabad ]]></addr-line>
<country>Pakistan</country>
</aff>
<aff id="Af6">
<institution><![CDATA[,COMSATS Institute of Information Technology Department of Meteorology ]]></institution>
<addr-line><![CDATA[Islamabad ]]></addr-line>
<country>Pakistan</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>06</month>
<year>2018</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>06</month>
<year>2018</year>
</pub-date>
<volume>57</volume>
<numero>2</numero>
<fpage>151</fpage>
<lpage>160</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_arttext&amp;pid=S0016-71692018000200151&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_abstract&amp;pid=S0016-71692018000200151&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_pdf&amp;pid=S0016-71692018000200151&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="en"><p><![CDATA[Abstract Porosity and water saturation are among the important reservoir parameters in terms of reservoir monitoring which in turn are necessary for placement of future production wells. Amplitude versus offset (AVO) modelling and analysis technique have been utilized for quantitative interpretation of porosity and water saturation. For AVO modeling, Gassmann fluid substitution model in connection with 2D seismic angle gathers were used for reservoir monitoring over Sawan-4 and Sawan-7 wells. AVO modelling results showed significant increase of density log by substituting gas by water, moderate increase of P-wave velocity and no change in S-wave velocity. Moreover, AVO modelling proved a strong relationship between porosity and reflection amplitude for all offset ranges. The class IV anomaly was evident for all porosities down to 5%. From fluid substitution modelling it is evident that changes in water saturation do not change the AVO effect significantly which further substantiate by investigation of pre-stack time migration (PSTM) gathers verifying the modelling results. The amplitude relationship between Sawan-4 and Sawan-7 is close to the modelled result. The amplitude and the AVO behaviour indicate lower porosity or significantly reduced sand thickness in the vicinity of Sawan-4 and Sawan-7 wells.]]></p></abstract>
<abstract abstract-type="short" xml:lang="es"><p><![CDATA[Resumen En términos de monitoreo los parámetros importantes del yacimiento son la porosidad y la saturación de agua, que a su vez son necesarios para la ubicación de futuros pozos de producción. La técnica de modelado y análisis de amplitud versus compensación (AVO, por sus siglas en inglés) se ha utilizado para la interpretación cuantitativa de la porosidad y la saturación de agua. Gassmann utilizó, para el modelado AVO, el modelo de sustitución de fluidos en conexión con recolectores de ángulo sísmico 2D para el control de yacimientos sobre los pozos Sawan-4 y Sawan-7. Los resultados del modelo de AVO mostraron un aumento significativo del registro de densidad al sustituir el gas por agua, además del aumento moderado de la velocidad de la onda P y ningún cambio en la velocidad de la onda S. El modelado AVO demostró una fuerte relación entre la porosidad y la amplitud de reflexión para todos los rangos de desplazamiento. La anomalía de clase IV fue evidente para todas las porosidades hasta el 5%. A partir del modelado por sustitución de fluidos se hizo evidente que los cambios en la saturación de agua no modifican significativamente el efecto AVO, lo cual se corrobora mediante la investigación de la migración de tiempo previo a la acumulación (PSTM), el cual verifica los resultados del modelado. La relación de amplitud entre Sawan-4 y Sawan-7 está cerca del resultado modelado. La amplitud y el comportamiento de AVO indican una menor porosidad o un espesor de arena significativamente reducido en la vecindad de los pozos Sawan-4 y Sawan-7.]]></p></abstract>
<kwd-group>
<kwd lng="es"><![CDATA[modelado de amplitud contra desplazamiento (AVO)]]></kwd>
<kwd lng="es"><![CDATA[sustitución de fluidos]]></kwd>
<kwd lng="es"><![CDATA[parámetros del depósito]]></kwd>
<kwd lng="es"><![CDATA[interpretación cuantitativa]]></kwd>
<kwd lng="es"><![CDATA[respuesta sísmica]]></kwd>
<kwd lng="es"><![CDATA[campo de gas Sawan]]></kwd>
<kwd lng="en"><![CDATA[Amplitude versus offset (AVO) modelling]]></kwd>
<kwd lng="en"><![CDATA[Fluid substitution]]></kwd>
<kwd lng="en"><![CDATA[Reservoir parameters]]></kwd>
<kwd lng="en"><![CDATA[Quantitative interpretation]]></kwd>
<kwd lng="en"><![CDATA[Seismic response]]></kwd>
<kwd lng="en"><![CDATA[Sawan gas field]]></kwd>
</kwd-group>
</article-meta>
</front><back>
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