Pacific Section AAPG, SPE and SEPM Joint Technical Conference

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Evaluation Of Three Mid-Cenozoic Sandstone Reservoirs In The San Joaquin Valley For Potential Carbon Storage

Abstract

Potential carbon storage reservoirs exist in mature oilfields of the southern San Joaquin Valley, California. Data regarding fluid extraction and injection and reservoir pressure exist for the three main oil reservoirs with carbon storage potential: the Stevens Sandstone member of the Monterey Formation, Vedder and Temblor formations. The pressure response of these reservoirs to fluid volume changes over time provides information regarding how carbon storage may affect the pressure gradients in the adjacent saline aquifers outside the fields where less data exist. This project may provide a template for analysis of other potential carbon storage reservoirs that are contiguous with oilfields. A field-scale version of the productivity index (PI, defined as the average net fluid production rate divided by the average pressure drop over the time period) was calculated for fields with substantial production from depths suitable for carbon storage. The PI determines the reservoir's pressure response to fluid production and is related to the effective CO2 storage capacity. The variance of the 2005 pressure values within each reservoir provides a measure of reservoir continuity. The highest PI values (113,000 and 88,410 m3/yr/MPa) occur in the Vedder Formation and the lowest occur in the Temblor Formation (3734 to 16,460 m3/yr/MPa). This indicates the Vedder reservoirs have more pressure support from the aquifer beyond the field than do the Temblor reservoirs. The greatest variance (8.5 MPa) occurs within the Temblor Formation in the Carneros unit of the Railroad Gap field and the pressure variance of 3.2 MPa within the Vedder Formation in the Greeley Field is the lowest. This indicates greater reservoir uniformity in the Vedder and more compartmentalization in the Temblor. Pressure response in the Stevens Sandstone is more varied within the two fields examined in this study (North and South Coles Levee) and appears to be directly related to the strategy used for pressure maintenance in the reservoirs. The lack of water production in the Stevens reservoirs suggests they receive minimal aquifer pressure support. The amount of carbon that could be stored is assumed to be equal to the amount of net fluid production in each of the fields for the purposes of this study. Potential storage values ranged from 44 million metric tons at South Coles Levee to eight million metric tons in the Carneros reservoir at Railroad Gap.