A 3-D Geostatistical Model of a Turbidite Reservoir and Validation by Pressure Transient Analysis

Abstract

This Paper was selected for presentation by lhe SPE Program CommifteaIol!owmg rewew 01 bnlofmnttcm .wnta,nsd m the abstract submitted by tha author(s) Contents of the paper as presented, have not be. rewewcd by the Socmiy of Pe!roleum Engineers and are subject 10 mrmcthm by th~author(s) The muterlal, as presented dcms not necessnrliy reflect any poa!tux of the Scwefy of Petroleum Engineers or IIS members. Papers presented at SPE meebngs are aubj~t 10 publ)catwn rewew by Edtiorml Comm!tlee o! Ihe Society O{ Pelraleum Eng!neers Permission 10 cow IS mslr$cted 10 an abstract cd not mom that 3131 words Illustrations may not be cowed. TIM abstract should ccmtaw conspicuous acknowfe&gemerd d wt,ere and~mom lhe paper was presented Wwe Llbranan, SPE, P O 8333836, Richardson, TX 750S3-3836 USA, i aX 01.2 !4.952.9435Abstract This paper gives details of an oil field reservoired in a turbidite sandstone fan in the North Sea. The majority of the field is characterised by a channelised, high densi{y turbidi(e system of high net-to-gross sandstones. Associated with these sand-rich channel fairways are lower net-to-gross fairway margin and interchannel areas. A review of the conventional geological mapping originally used for the subject field has shown that this heterogeneity is not captured in (he current deterministic geological model.The objective of the 3D modelling was to address this complexity early in the field life. A hierarchical geostatistical model has been develo@ to create detailed 3D reservoir models for the reservoir interval. Initially the reservoir has been divided deterministically into the three different domains of channel axis, channel margin and interchannel by using seismic attribute data, Sequential indicator simulation was used to distribute reservoir facies within each domain, The reservoir facies were characterised using core, wireline log and sedimentological data, During model construction, each domain is conditioned to adjacent domains to ensure geological sensible continuity across any interchannel to channel margin to channel axis transect. Vertical variogram models were derived from well log and core data.Outcrop data were used to constrain the required variogram anisotropy for the horizontal variogram models. Sequential Gaussian simulation was used to populate the facies description with appropriate porosity and permeability values, Following generation of the 3-D geological model, numerical pressure transient analysis was used to validate the reservoir model. By iteration of model parameters, the pressure transient description was honoured for a number of wells. Consequently, integration of pressure transient data has created a more robust reservoir model, and has highlighted unresolved uncertainties.