پیش‌بینی فشارمنفذی در مخازن کربناته با استفاده از سرعت لرزه‌ای برآورد شده از آنالیز چند نشانگری

اﻣﺮوزه از روش ﻫﺎی ﻣﺘﻔﺎوﺗﯽ ﺑﺮای ﭘﯿﺶ ﺑﯿﻨﯽ ﻓﺸﺎر ﻣﻨﻔﺬی اﺳﺘﻔﺎده ﻣﯽ ﺷﻮد ﮐﻪ ﻫﺮ ﯾﮏ ﻧﻘﺎط ﻗﻮت و ﺿﻌﻒ وﯾﮋه ای دارﻧﺪ. در اﯾﻦ ﺗﺤﻘﯿﻖ ﻓﺸﺎر ﻣﻨﻔﺬی و ﻣﮑﺎﻧﯿﺰم ﻫﺎی ﻣﺮﺑﻮط در ﯾﮑﯽ از ﻣﺨﺎزن ﻫﯿﺪروﮐﺮﺑﻨﯽ ﮐﺮﺑﻨﺎﺗﻪ ﺟﻨﻮب ﻏﺮب اﯾﺮان ﺑﺎ اﺳﺘﻔﺎده از روش ﺳﺮﻋﺖ ﻟﺮزه ای ﻣﻮرد ﺑﺮرﺳﯽ و ﺗﺨﻤﯿﻦ ﻗﺮار ﮔﺮﻓﺘﻪ اﺳﺖ. ﺑﺮای اﯾﻦ ﻣﻨﻈﻮر ﺳﺮﻋﺖ ﺑﺎزه ﻟﺮزه ای ﺑﺎ اﺳﺘﻔﺎده از روش آﻧﺎﻟﯿﺰ ﭼﻨﺪ ﻧﺸﺎﻧﮕﺮ ی ﻟﺮزه ای ﺑﻪ دﺳﺖ آورده ﺷﺪ. ﻣﮑﻌﺐ ﻓﺸﺎر روﺑﺎره ﻫﻢ از ﻣﮑﻌﺐ ﭼﮕﺎﻟﯽ ﺗﺨﻤﯿﻦ زده ﺷﺪ. ﺑﺮای ﺗﺤﻠﯿﻞ ﻣﮑﺎﻧﯿﺰم ﻫﺎی ﻣﻮﺛﺮ در ﻓﺸﺎر ﻣﻨﻔﺬی، ﺑﺎ ﺗﺮﺳﯿﻢ ﻧﻤﻮدار ﻣﺘﻘﺎﻃﻊ ﺳﺮﻋﺖ- ﭼﮕﺎﻟﯽ ﺑﺎﻟﮏ در ﭼﺎه ﻫﺎی ﻣﯿﺪان، ﻧﺸﺎن داده ﺷﺪ ﮐﻪ ﻣﮑﺎﻧﯿﺰم اﺻﻠﯽ ﻣﻮﺛﺮ در ﻓﺸﺎر ﻣﺨﺰﻧﯽ، ﺗﺮاﮐﻢ ﻧﺎﻣﺘﻮازن ﺑﻮده اﺳﺖ. ﺑﻨﺎﺑﺮاﯾﻦ راﺑﻄﻪ اوﻟﯿﻪ ﺗﺒﺪﯾﻞ ﺳﺮﻋﺖ ﺑﻪ ﻓﺸﺎر از ﺑﺮازش ﺑﯿﻦ داده ﻫﺎی ﻓﺸﺎر ﻣﻮﺛﺮ و ﺳﺮﻋﺖ ﻟﺮزه ای ﺑﻪ دﺳﺖ آورده ﺷﺪ. ﭘﺲ از ﮐﺎﻟﯿﺒﺮاﺳﯿﻮن در ﻣﺤﻞ ﭼﺎه ﻫﺎ، ﺿﺮاﯾﺐ راﺑﻄﻪ ﻧﻬﺎﯾﯽ ﺷﺪه و داده ﻫﺎی ﺳﺮﻋﺖ ﺑﻪ ﺗﻨﺶ ﻣﻮﺛﺮ ﺑﺮﮔﺮداﻧﺪه ﺷﺪ. ﺳﭙﺲ ﻣﮑﻌﺐ ﺗﻨﺶ ﻣﻮﺛﺮ ﺑﺎ اﺳﺘﻔﺎده از راﺑﻄﻪ ﺗﺮزاﻓﯽ ﺑﻪ ﻣﮑﻌﺐ ﻓﺸﺎر ﻣﻨﻔﺬی ﺗﺒﺪﯾﻞ ﺷﺪ. ﺑﺮرﺳﯽ ﻣﻘﺎﻃﻊ ﻋﺮﺿﯽ ﺗﻬﯿﻪ ﺷﺪه از ﻣﮑﻌﺐ ﻓﺸﺎر ﻣﻨﻔﺬی، ﺑﯿﺎﻧﮕﺮ ﺗﻔﮑﯿﮏ واﺿﺢ ﻻﯾﻪ ﻫﺎی ﻣﺨﺰﻧﯽ از ﺑﺨﺶ ﻫﺎی ﺑﺎﻻ و ﭘﺎﯾﯿﻦ ﺧﻮد اﺳﺖ. ﻫﻤﭽﻨﯿﻦ ﺗﺠﺰﯾﻪ ﺗﺤﻠﯿﻞ آﻣﺎری ﻧﺘﺎﯾﺞ ﺗﺤﻘﯿﻖ اﻋﻢ از ﺧﻄﺎی ﻣﯿﺎﻧﮕﯿﻦ ﻣﺮﺑﻌﺎت ﮐﻢ و ﺿﺮﯾﺐ ﻫﻤﺒﺴﺘﮕﯽ ﺑﺎﻻ ﺑﯿﻦ داده ﻫﺎی ﭘﯿﺶ ﺑﯿﻨﯽ ﺷﺪه و واﻗﻌﯽ، ﻧﺸﺎن ﻣﯽ دﻫﺪ ﮐﻪ روش ﺳﺮﻋﺖ ﻟﺮزه ای ﺣﺎﺻﻞ از آﻧﺎﻟﯿﺰ ﭼﻨﺪ ﻧﺸﺎﻧﮕﺮی ﻗﺎدر اﺳﺖ ﻓﺸﺎر ﻣﻨﻔﺬی را ﻗﺒﻞ از ﺣﻔﺎری در ﺳﺎزﻧﺪﻫﺎی ﮐﺮﺑﻨﺎﺗﻪ ﺑﻪ ﺻﻮرت ﻗﺎﺑﻞ ﻗﺒﻮﻟﯽ ﭘﯿﺶ ﺑﯿﻨﯽ ﮐﻨﺪ. ﺑﻨﺎﺑﺮاﯾﻦ اﻧﺠﺎم اﯾﻦ ﻣﻄﺎﻟﻌﺎت ﻣﯽ ﺗﻮاﻧﺪ در ﺗﻌﯿﯿﻦ وزن ﮔﻞ ﺣﻔﺎری، ارزﯾﺎﺑﯽ ﭘﺘﺎﻧﺴﯿﻞ ﺧﻄﺮ و اﻗﺘﺼﺎد ﺣﻔﺎری اﻫﻤﯿﺖ ﻗﺎﺑﻞ ﻣﻼﺣﻈﻪ ای داﺷﺘﻪ ﺑﺎﺷﺪ.

Pore pressure prediction using the seismic velocity produced by multiattributes analysis in carbonate reservoirs

There are various methods for pore pressure prediction in hydrocarbon (HC) reservoirs which have their advantages and disadvantages. Herein seismic velocity was used to evaluate the pore pressures in one of the Iranian HC reservoirs along with its creation mechanisms. Seismic velocity was derived by seismic multiattributes analysis method, to study interval velocities. The overburden pressure cube was estimated from the density cube. Thereafter effective pressures were obtained with Terzaghi equation at well locations by using well pressure tests (RFT) and overburden pressures. The velocitydensity crossplots represent that disequilibrium compaction is the main mechanism of pore pressure creation. Thus, an initial relationship was obtained by fitting of the effective pressure and seismic velocity data and it was then used for determining the calibration coefficients required for conversion of seismic velocity cube to the effective pressure cube. Finally, the effective pressure cube was converted to pore pressure cube by Terzaghi equation. The obtained results with high consistency, high correlation coefficient and low mean squares error indicate that pore pressures could be perfectly predicted by multiseismic attributes method in carbonate formation before drilling. Moreover, comparative studies of the pore pressure cube estimated from the proposed model indicates that the pore pressure model obtained by multiattribute analysis is precise enough to separate the reservoir layers from its upper and lower sections. This predicted pore pressure can be used to evaluate the drilling risk and also to estimate the required mud weights.