Study of Hydrodynamic Activity in the Mishrif Fields Offshore Iran
Authors: Pelissier Jean , Hedayati Ali Akbar , Abgrall Edouard , Plique Jacques 
Published: December 2007

Pelissier, Jean, SPE, Pelissier, Jean, SPE, Societe Nationale Elf Aquitaine (P) Hedayati, Ali Akbar, SOFRAN Abgrall, Edouard, Societe Nationale Elf Aquitaine (P) Plique, Jacques, Plique, Jacques, Societe Nationale Elf Aquitaine (P)

A sharply tilted water/oil contact was encountered in two Iranian fields, Sirri-D and Sirri-C, confirming strong hydrodynamic-activity in reservoir, offshore Iran. Studies of remaining oil on cores showed discrepancies related to the water/oil interface. These results and a mathematical model enabled determination of the water/oil contact of a nearby oilfield, Sirri-E, with good probability.

Introduction

The discovery of the Sirri-E field offshore Iran is too recent for its oil/water contact to be known. However, the existence of aquifer activity in the fields of this region has been proved in the last few years from the results of well tests, and an isopotential map has been drawn.The development of the Sirri-D and Sirri-C fields in the Mishrif formation permitted an evaluation of the importance of aquifer activity in this area from the existence of a particularly high dip of the oil/water contact.A novel method of geochemical analysis of residual oils in some Sirri-D cores reveals marked modifications in the compositions of these oils induced by aquifer activity. This permitted the characterization and accurate location of the oil/water contact in two particular wells.To derive the probable form of the oil/water contact for Sirri-E, a model of the basin was built to match the flow of the aquifer based on the isopotential curves around Sirri-D and Sirri-C.

Knowledge of Aquifer Activity Provided by Sirri-D and Sirri-C Provided by Sirri-D and Sirri-C The pressure measurements recorded in the fields offshore Iran show a distribution of isopotentials corresponding to groundwater flow within the aquifers from the shore of the gulf to a central outlet (Fig. 1). The Fateh and Sirri fields, producing from the Mishrif formation, are within the framework of this aquifer activity and show particularly steep oil/water interfaces. In the Sirri region, the general direction of the flow seems to be approximately southwest to northeast with a south-north alignment near the reservoir limit west of Sirri-D and Sirri-C.

Sirri - D

The Sirri-D (Fig. 2) discovery well, SiD-1, on the northwest flank of the structure, encountered the oil/water contact at 2510 m below sea level. At the same time in 1972, an appraisal well, SiD-2, confirmed the existence of only oil at the top of the structure.

Field development started in 1975 and showed the existence of a tilted oil/water contact dipping generally from south to north with dips up to 12/1,000, particularly on the western flank of the structure.The reservoir rock is a wackestone/packstone limestone, gray to whitish, with many thin laminated shale. The rock includes bioclastic fragments and cracks infilled with sparry calcite. Dolomite rhombs appear downward. In thin section, the low porosity is located between the micrite crystals and in some cracks.

JPT

P. 1043