Bioturbation enhanced petrophysical properties in the Ordovician carbonate reservoir of the Tahe oilfield, Tarim Basin, NW China

Niu, Yongbin; Cheng, Man; Zhang, Li‐Jun; Zhong, Jian; Liu, Shengxin; Wei, Duan; Xu, Zi-Lu; Wang, Peijun

doi:10.1016/j.jop.2022.01.001

Cited by 14 publications

(6 citation statements)

References 52 publications

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“…Diagenetic phases of carbonate rocks of the Yingshan Formation from subsurfaces and outcrop analogues are characterized by mechanical and chemical compaction, cementation, dissolution, dolomitization, and micritization (Niu et al, 2010). The timing of each diagenetic process is shown in Figure 3.…”

Section: Structural Evolutionmentioning

confidence: 99%

Relationship between stylolite morphology and the sealing potential of stylolite-bearing carbonate cap rocks

Fan

Gomez‐Rivas

et al. 2022

GSA Bulletin

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We analyzed the sealing effectiveness of cap rocks bearing different types of stylolites using a combination of petrographic, petrophysical, pore structure, and sealing capacity characterization techniques. This study was based on examples of carbonate cap rocks that seal ultradeep hydrocarbon reservoirs of the Tarim Basin (China). Samples from both drill cores and their outcrop analogues were investigated to quantify how morphology influences the sealing capacity of different types of stylolite-bearing rocks. The study cap rocks consisted of mudstone, wackestone to packstone, grainstone, and dolomitic limestone. Four types of stylolites were identified: rectangular layer, seismogram pinning, suture and sharp peak, and simple wave-like types. The difference in the sealing capacity of carbonate cap rocks is attributed to their pore structure connections and the types of stylolites they develop. Samples bearing simple wave-like stylolites showed the best sealing capacity, followed by those with rectangular layer and suture and sharp peak types, whereas carbonates hosting seismogram pinning types had the lowest sealing capacity. The impact of stylolite segments on the rock sealing properties, however, differed from one segment to another. Rectangular layer−type stylolites could be divided into three distinct segments (with good, moderate, and poor sealing, respectively). Both the seismogram pinning and suture and sharp peak stylolite types were divided in two parts, with the former one having moderate and poor sealing and the latter exhibiting good and moderate sealing. The simple-wave−like type had a good sealing capacity all along the pressure-solution seam. The most effective sealing barriers for vertical fluid flow form when (1) calcite and siliceous cements are pervasively distributed in the vicinity of stylolites, forming highly cemented zones with lower porosity and permeability than their surrounding host rocks; (2) stylolites are enriched in insoluble residues; and (3) rare microfractures and dissolution vugs are found along the stylolites. This work provides useful examples for the prediction of the sealing potential of stylolite-bearing carbonate rocks according to stylolite morphology in other geologic settings.

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Section: Structural Evolutionmentioning

confidence: 99%

Relationship between stylolite morphology and the sealing potential of stylolite-bearing carbonate cap rocks

Fan

Gomez‐Rivas

et al. 2022

GSA Bulletin

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“…7 The buried depth of the reservoir is below 5500 m, with a high temperature (130 °C) and high salinity (>20 × 10 4 mg/L). 8,9 At present, the proven oil and gas reserves are more than 12.66 × 10 8 t. 10 The oil and gas reserves in the Ordovician carbonate reservoir account for more than 90% of the total reserves, which is the largest in the world.…”

Section: Introductionmentioning

confidence: 99%

“…Its Ordovician carbonate reservoir environment is dominated by fracture type, karst cave type, and fracture–fracture cave type, which belongs to the fractured depression reservoir with strong heterogeneity . The buried depth of the reservoir is below 5500 m, with a high temperature (130 °C) and high salinity (>20 × 10 4 mg/L). , At present, the proven oil and gas reserves are more than 12.66 × 10 8 t . The oil and gas reserves in the Ordovician carbonate reservoir account for more than 90% of the total reserves, which is the largest in the world.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Polyvinyl Alcohol–Phenolic Aldehyde–Polyacrylamide Gel for the Application in Saline Oil Reservoirs for Profile Modification

Dong,

He,

et al. 2023

Energy Fuels

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Polymer gels are widely used in the oil and gas industry, and high-molecular-weight polymer gels have significant effects on reservoir water plugging operations. Based on nontoxic polyvinyl alcohol (PVA), its stability in solvents containing formation saltwater (Tahe oilfield, NW China) was studied, and the composite gel solution was prepared using saltwater. The polymerization mechanism of PVA with phenolic resin (PF) and polyacrylamide (PAM) was analyzed, using hexamethylenetetramine (HMTA) instead of formaldehyde for cross-linking, and the rheological properties of the prepared gel were tested; the results showed excellent elastic properties. The application value of the gel was evaluated by gelation performance, thermal stability, and indoor simulated core displacement. The gelation time of the PVA/PAM/PF gel at 130 °C was 4 h; after aging at 130 °C for 40 days, the gel strength of the polymer gel remained at the G level, and no dehydration occurred. The simulated core plugging results showed that the breakthrough pressure was 11.79 MPa and the plugging rate was 99.83%. Compared with the PAM/PF gel, the PVA/PAM/PF gel has a higher breakthrough pressure, which is beneficial to reduce the permeability of the porous medium.

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“…Consequently, burrows commonly experience distinct diagenetic paragenetic sequences and generate distinguishing rock fabrics and physical properties compared to matrices (Pemberton & Gingras, 2005; Hollis, 2011; Corlett & Jones, 2012; Liu et al ., 2019). Many reservoirs globally have some sort of bioturbation, which impacts their capacity to produce economic amounts of hydrocarbons (Gingras et al ., 2004a, 2012; Pemberton & Gingras, 2005; Baniak et al ., 2013, 2022; Knaust, 2014; Liu et al ., 2019; Eltom et al ., 2021; Niu et al ., 2022).…”

Section: Introductionmentioning

confidence: 99%

High‐magnesium calcite skeletons provide magnesium for burrow‐selective dolomitization in Cretaceous carbonates

Liu,

Shi,

Liu

et al. 2023

Sedimentology

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The source and pumping mechanism of magnesium play crucial roles in dolomitization. The preferential dolomitization of burrows has been extensively documented in geological archives. Although burrows are abundantly preserved in Cretaceous carbonates, burrow‐selective dolomitization is uncommon in normal salinity marine environments due to low Mg/Ca ratio of seawater. However, burrow‐selective dolomitization occurred in the Cenomanian Rumaila Formation carbonates of the Arabian Platform providing an excellent example to further clarify the mechanism and explore other potential Mg sources of burrow‐elective dolomitization. Integrated studies of petrography, stable isotope geochemistry and laser ablation‐inductively coupled plasma‐mass spectrometry‐based in situ element geochemistry were conducted. It was found that the burrow‐selective dolomitization exclusively occurred in echinoderm fragments‐filled Thalassinoides networks occurred as Glossifungites ichnofacies. Burrow dolomites showed fine to medium crystalline and planar subhedral to euhedral textures with cloudy centres and clear rims. They exhibited relatively greater Mn, lower Sr and Fe concentrations, no or very weak negative Ce anomaly and middle rare earth element‐bulge patterns, and are slightly enriched with occasionally depleted δ13C and comparable δ18O relative to the surrounding calcite matrix. The initial high‐Mg calcite echinoderm fragments in burrows have been stabilized to low‐Mg calcite, and echinoderm syntaxial overgrowth calcite cement was practically nonexistent. Echinoderm fragments were frequently replaced by dolomite in part or whole. Undolomitized echinoderms have negative Ce anomaly and seawater‐like rare earth element patterns, as well as very low Mn, Fe and relatively greater Sr concentrations. These suggest that echinoderm stabilization occurred in fluid unsaturated with respect to high‐Mg calcite driven by aerobic decomposition of organic matter in oxic seawater near sediment‐water interface, meanwhile, Mg ions were liberated into pore water. This process predated the dolomitization allowing the Mg derived from echinoderm to raise the Mg/Ca ratio of burrow interstitial water. The dolomites in burrows were generated by initial replacement and subsequent overgrowth cementation associated with bacterial sulphate reduction and methanogenesis in low‐temperature and suboxic to anoxic fluids in near‐surface realm, and faintly recrystallized as burial depth increased. This study sheds light on the echinoderm stabilization process, links the early diagenesis of skeletons to burrow dolomitization, and proposes a conceptual model illustrating that high‐Mg calcite skeletons could act as a major Mg source for burrow‐selective dolomitization, which compensates for the deficiency of Mg in normal low Mg/Ca ratio Cretaceous seawater. This study implies the interaction effect and element cycle among components in early diagenetic systems, and verifies that high‐Mg calcite is indeed a non‐negligible potential Mg source for partial or elective dolomitization.

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Bioturbation enhanced petrophysical properties in the Ordovician carbonate reservoir of the Tahe oilfield, Tarim Basin, NW China

Cited by 14 publications

References 52 publications

Relationship between stylolite morphology and the sealing potential of stylolite-bearing carbonate cap rocks

Relationship between stylolite morphology and the sealing potential of stylolite-bearing carbonate cap rocks

Investigation of Polyvinyl Alcohol–Phenolic Aldehyde–Polyacrylamide Gel for the Application in Saline Oil Reservoirs for Profile Modification

High‐magnesium calcite skeletons provide magnesium for burrow‐selective dolomitization in Cretaceous carbonates

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