STRUCUTURAL AND GEOMECHANICAL ANALYSIS TO PREDICT NATURALLY FRACTURE CARBONATE RESERVOIR CAHARACTERIZATION OF WHF FIELD, BANGGAI BASIN, INDONESIA

Abstract

The  WFH  field  has  been  in  production  since  2005  with  reserves  of  120  MMBO  and  has  reached  peak production of up to 4000 BOPD. The reservoir rock from this field is Miocene Bioclastic Limestone with an average matrix porosity of 8% and a water saturation of 13%. Based on the results of the core rock study and analysis of well production tests, the reservoir in the WFH field indicates the presence of natural fractures that control porosity and permeability  so  that  a  mechanical  approach  such  as  structural  and  geomechanical  analysis  is  needed  to  get  an understanding of characteristics and distribution of natural fractures that the resolution is under seismic resolution.Geological  structure parameters are obtained  from the sesimic  interpretation of reservoir horizon and several  faults then reconstructed to obtain the strain value from this field. Geomechanical properties such as the stress regime in the WFH field are obtained from theresults of stress analysis. The stress analysis shows that the WFH field is in a normal fault  regime  (Sv>  SHmax>  Shmin).  Structural  reconstrution  analysis  showed  a  vertical  strain  value  is  18%  and horizontal strain value is -17%. This value is obtained from the sum of the movement of reservoir in the thrust fault plane. The  slope  modeling of the simulated  fracture ranges  from 35 to 40 degrees which  is  identical to the natural fracture observations obtained from the log image interpretation. The intensity of fractures in the WFH field reservoir is  in  the  area  around  the  fault  plane,  especially  in  the  bend  area.  In  addition,  the  intensity  of  fractures  that  could potentially open is indicated by a large Slip Tendency value of 0.4. The incorporation of areas with high slip tendency and fracture instensity resulted in an open natural fracture zone in this reservoir trending NW-SE which is associated with factoring faults that are identical to the trend of the WFH field structure.Modeling from this subsurface data is expected  to  be  able  to  build  a  reliable  geological  and  geomechanical  structure  model  to  provide  the  best recommendations for the placement of further wells and as an analogy in reducing the risk of exploration in a similar play