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Integrated Modeling
of the Taratunich Field, Bay of Campeche,
Southern Mexico*
By
W.J. Clark1, F.O. Iwere1, O. Apaydin1, J. Moreno1, R. Leon Ventura2, R. Hernandez2, J. Garcia2, and F. Trevino3
Search and Discovery Article #20014 (2003)
*Adapted from “extended abstract” for presentation at the AAPG Annual Meeting, Salt Lake City, Utah, May 11-14, 2003.
1Schlumberger DCS, Greenwood Village, Colorado ([email protected])
2Pemex, Dos Bocas, Mexico
3Pemex, C. del Carmen, Mexico
Introduction
Taratunich Field is located about 80 km northwest of Ciudad del Carmen in the Bay of Campeche, southern Mexico and is part of a series of prolific oil reservoirs that include Cantarell and Abkatun-Pol-Chuc fields (Figure 1). Since its discovery in 1989, the field has produced over 150 MMSTB of oil from Jurassic and Cretaceous/Paleocene carbonates. A multidisciplinary team consisting of engineers, geologists, geophysicists and petrophysicists was assembled to characterize and simulate the Taratunich Field with the objective of developing a reservoir management plan that would increase daily production and ultimate recovery. The following documents the methodologies used and the results from this effort.
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GeologyThe geologic structure of Taratunich field is a doubly plunging, WNW-ESE aligned, reverse-faulted antiform with a salt piercement diapir/swell at the center of the structure (Figure 2), as mapped from a 3-D seismic survey and verified by well data. Two normal faults are present over the area of the salt piercement structure and are oriented nearly perpendicular to the reverse faults, creating a small graben over the salt dome. No wells exist in the block to verify the seismic correlations. The field is divided into separate compartments by the faults, which are designated blocks 101-401 (Figure 2). Two wells have crossed the southern reverse fault(s), but there is no oil production from the areas south of the main field. There is, however, oil production from block 101, north of block 201 and the northern reverse fault. No wells penetrate the faulted compartment north of block 301 as water is expected in this block because of the lower structural position NW of block 101. A generalized stratigraphic column for the Bay of Campeche is shown in Figure 3. Production is from a thick (>750 m) Jurassic (Kimmeridgian) oolitic grainstone unit that has been dolomitized in part, and a thinner (60-120m) sedimentary gravity flow breccia and grainstone interval of Late Cretaceous to Paleocene age (‘‘Brecha’’ Formation). The diapir is interpreted to have completely penetrated the Kimmeridgian and at least part of the overlying Tithonian section. Movement of the salt probably took place during Late Jurassic and Early Cretaceous times. Thinning of the Tithonian through Paleocene sections toward the salt dome provides evidence of a paleotopographic high that formed as a response to synsedimentary salt movement. The Kimmeridgian section (JsK) consists of peloidal, oolitic, and pisolitic grainstones that were almost completely dolomitized on the western side of the salt swell (block 301). To the east (blocks 101 and 201), the JsK is comprised of tightly cemented limestones. The JsK was subdivided into 6 major shallowing-upward sequences bounded by maximum-flooding surfaces. In the upper reservoir intervals (where most log data were available), sequences were further subdivided into parasequence sets based on internal-flooding surfaces (Figure 3). Shale is more prominent in blocks 101 and 201 and served as the basis for defining the sequences in these areas. Dolomitization in block 301 was accompanied by dissolution of the original clasts and the development of round moldic pores. Moldic pores range from about 1mm to 5mm, are generally are not touching, and are connected by intercrystalline dolomite pores and microfractures. No moldic pores are present in the limestone. The Tithonian consists of argillaceous and silty/sandy, deep-water limestones. The Cretaceous section is pelagic lime mudstones with grainstone and organic-rich beds in the Upper Cretaceous section. The ‘‘Brecha’’ interval (BPT-Ks: Figure 3) consists of coarse mud-matrix breccia facies of debris-flow origin, channelized and non-channelized skeletal grainstones interpreted as turbidite flows, and pelagic mudstones. Debris for the gravity deposits was derived from the collapsing carbonate platform to the east of Taratunich field in the Yucatan area.
PorosityThree porosity types were identified in varying proportions in each reservoir: matrix, vugs, and fractures. Routine core analysis, neutron magnetic resonance (NMR), and capillary-pressure tests provided matrix and vug porosity and permeability, and wireline logs provided matrix and some portion of vug and fracture porosity. Oomoldic porosity in the JsK was a challenge to quantify, and image-log techniques were used to estimate this porosity. The reservoir model was prepared for dual porosity flow simulation by combining matrix and non-connected vugs into one component and fractures and connected vugs into the other component. Property maps including all porosity types, thickness, net, and log-derived permeability were prepared for each reservoir layer, upscaled and input into the reservoir simulator.
Fracture
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