The Cretaceous in Well Ye Yun 2 is 3 19m thick, mainly composed of thick grayish brown glutenite, gravelly sandstone and thin grayish brown powder, fine sandstone and mudstone. The reservoir lithology is mainly gravelly sandstone and glutenite with a thickness of176m. Followed by silty and fine sandstone, with a thickness of 37m. From the core observation, the sandstone has poor sorting, high impurity content and large particle size change, and the gravel diameter is generally 2 ~ 3 cm, which indicates that it is the product of rapid accumulation under the sedimentary environment of alluvial fan-fan delta plain.
Figure 5- Triangle Diagram of Cretaceous Rock Types in Ye Yun 2+0 1 Well
The Cretaceous coring interval is 5986.65 ~ 607 1.08 m, and the main rock types are limestone-bearing fine-grained lithic sandstone and limestone fine-grained lithic sandstone; The 6071.08m interval is coarse-medium grained lithic sandstone (Figure 5- 1 1).
The timely content of clastic components is 44% ~ 63%, with an average of 55.8%. The feldspar content is 6% ~ 15%, with an average of 9.6%; The content of cuttings is 27 ~ 50%, with an average of 34.3%. The composition of cuttings is complex, mainly including quartzite, phyllite, volcanic rock and schist. At the same time, a small amount of siliceous rocks are seen, and some cuttings are argillaceous. The filler content is 13% ~ 38%, with an average of 22.20%. Calcite content is 5% ~ 30%, with an average of 65438 06.78%; The silt content is 3% ~ 8%, with an average of 5.65438 0%; See a small amount of timely secondary increase. The rock is quite dense, with an area ratio of 0 ~ 1% and an average of < 1%. Intracrystalline dissolved pores and microcracks are occasionally seen, with the pore size < 0.0 1 mm ... in the sections of 5993.25m and 607 1.08m, the granular clay film has asphalt adsorption, and calcite is filled outside the clay film. The content of illite/montmorillonite mixed layer of sandstone clay mineral is 0 ~ 69%, with an average of 50%; The content of illite is 2 1% ~ 24%, with an average of 57%. The content of kaolinite is 4% ~ 8%, with an average of 5.75%; The chlorite content is 5% ~ 7%, with an average of 5.5%; The ratio of Iraq/Mongolia mixed layer is 0 ~ 55%, with an average of 24.3%.
2. Rabbit-Yinan-Dina structural belt
According to outcrop and drilling data, only the Yagram Formation and He Shushan Formation of Kapshaliang Group are developed in Cretaceous in this area, but Bashi Kichik Formation and Basgai Formation are missing. The reservoir rocks are mainly medium conglomerate and medium sandstone, followed by fine sandstone and coarse sandstone, and siltstone reservoir is undeveloped. On the plane, the reservoir thickness of outcrop profile in Yiqixi area is less than 9m, and the reservoir rocks are mainly medium conglomerate. From the east to Tugeming area, the reservoir thickness increases, generally about 80m, and the reservoir granularity becomes finer, mainly sandstone, followed by medium conglomerate. Vertically, the lower member of this group is mainly medium conglomerate reservoir; The upper member is dominated by sandstone reservoirs, in which Yiqixi area is dominated by fine sandstone and Tugeming area is dominated by medium sandstone.
The composition maturity of sandstone in Yagelmu Formation is very low, and most of them are lithic sandstone. The seasonal content is 14. 1% ~ 36.4%, with an average of 25.6%. The feldspar content is 6.8% ~ 19.6%, with an average value of 10.9%. The content of drilling cuttings is 46% ~ 76.65438 0%, with an average of 63.4%. The average composition maturity is only 0.34. Sandstone is coarse in grain size, mainly composed of medium sand grains, with a small amount of coarse sand and fine sand grains, and the main grain size range is 0.25 ~1.00 mm; The sorting property is medium, the roundness is round-sub-round, and the particles are mostly point-and-line contact. Sandstone cementation type is porous, with medium structural maturity and well rounded particles, which may be related to wind transport. The content of interstitial materials in sandstone is low, generally ranging from10% to15%, mainly cementing materials, and the content of hetero groups is very low. There are (iron) argillaceous rocks and felsic rocks, and their contents are generally less than1%. The cement is mainly calcite, followed by dolomite, iron oxide and authigenic clay minerals. , the content is mostly 5% ~ 15%.
The reservoir rocks of He Shushan Formation are undeveloped, and the reservoir thickness is only 1 ~ 46m, accounting for 18.5% ~ 35% of the thickness. The reservoir rocks are mainly siltstone and argillaceous siltstone of lakeside sand bar. Horizontally, the grain size in Tugeming area is slightly coarser than that in Yiqixi area; Vertically, reservoir rocks are mainly distributed in the middle and upper parts, with a small single layer thickness and a slight reverse grain order change from bottom to top. Most sand bodies are isolated sand bodies with poor longitudinal connectivity and good lateral continuity. The composition maturity of He Shushan Formation reservoir is also low, almost all of which are lithic sandstone. The timely content is 16.5% ~ 29.8%, with an average of 26. 1%. The feldspar content is 10.6% ~ 15.6%, with an average of 10.9%. The content of cuttings is 56.2% ~ 72.4%, with an average of 6 1. 1%. The average component maturity index is only 0.36. Sandstone is mainly composed of silt and fine sand particles, the main silt range is 0.07~0.20mm, the sorting is medium or good, the roundness is sub-edge-sub-circle, the particles are in point-line contact, the membrane-pore cementation type, and the structural maturity is preferred. The total amount of (silty) sandstone fillings is generally 15% ~ 20%, mainly calcite cement, and the content is generally10% ~ 20%; A small amount of argillaceous heterobase, the content is generally about 65438 0%.
The content of debris is mainly metamorphic rock debris, followed by igneous rock debris, and there are few sedimentary debris, indicating that debris mainly comes from metamorphic rock area. Comprehensively, the Yakulumu Formation is a transitional type between the provenance of the cyclic orogenic belt and the provenance of the volcanic arc.
3. crassus structural belt
According to the analysis of a large number of core slices, the reservoir rocks of Cretaceous Bashi Kichik Formation in Kela 2 gas field are mainly brown medium-fine lithic sandstone, with an average time content of 46. 15% ~ 48.9%, feldspar (mainly potassium feldspar) with an average content of 9.34% ~ 16.02%, and cuttings (mainly metamorphic rock cuttings and sedimentary cuttings) For example, the 3477.04m interval of Well Kela 3 is feldspathic sandstone containing anhydrite secondary cuttings, of which the timely content is 56%, the feldspar content is 20% and the cuttings content is 24%. The authigenic minerals are anhydrite, calcite and dolomite, and a small amount of feldspar has a secondary increase. The formation sequence of authigenic minerals is dolomite-calcite-feldspar enlargement-anhydrite. Rock dissolution is relatively developed, mainly particle dissolution. Common pores are intergranular dissolved pores, intragranular dissolved pores and a few granular dissolved pores, and the pore size is 0.01~ 0.5 μ m. According to its clastic composition, the rock is named lithic sandstone (Figure 5- 12).
Fig. 5- Triangle Diagram of Kela2 Gas Field 12 Debris Component Content
Sandstone clastic particles are sub-angular-sub-circular, with medium-good sorting; Medium cementation, mostly pore cementation, a small amount of contact cementation, mosaic cementation and basement cementation; The particles are mainly point contact and line contact, showing the characteristics of medium to high structural maturity.
The interstitial materials of Bashi Kichik Formation sandstone in Kela 2 gas field are mainly matrix and cement. The content of heterobase is generally 6% ~ 9%, mainly argillaceous and iron muddy; Cement content is generally 2.5% ~ 9%, mainly dolomite, followed by calcite, a small amount of gypsum, siliceous and analcime, pyrite and so on.
4. Tubei and Dabei tectonic belts
The Cretaceous rocks in Tubei 1 Well are mainly limestone fine-grained lithic sandstone and anisometric lithic sandstone. The timely content of clastic components is 4 1% ~ 84%, with an average of 72.2%. The feldspar content is 10% ~ 17%, with an average of 9.6%; The content of cuttings is 28% ~ 42%, with an average of 28.4%. The main interstitial materials are argillaceous, calcite and analcime. The filler content is 14% ~ 57%, with an average of 23.2%; Calcite content is 5% ~ 65438 02%, with an average of 8.5%; The content of analcime is 2% ~ 8%, with an average of 3.3%. Local pores are well developed, including intergranular pores and intergranular dissolved pores, with a pore size of 0.01~ 0.1mm.
5. Erak tectonic belt
The intergranular matrix of Yilake structural belt is composed of argillaceous and iron mud, in which the iron mud is mainly distributed in the lower 5,320.44 ~ 5,709.53m interval. The types of clastic rocks in Upper Cretaceous reservoirs are mainly fine-grained feldspathic lithic sandstone and fine-grained lithic sandstone containing limestone, followed by limestone and medium-grained feldspathic lithic sandstone and lithic sandstone containing limestone, extremely fine-grained, medium-coarse grained feldspathic lithic sandstone and a small amount of gravelly medium-grained lithic sandstone. The lower part is mainly composed of gray and gray gravelly and gravelly medium-grained lithic sandstone, followed by gray conglomerate and gray fine sandstone with very fine-grained lithic sandstone. Among them, the content of sandstone components is: 4% ~ 70%, feldspar 1% ~ 23%, and cuttings 24% ~ 96%. The timely content gradually increased from top to bottom; The feldspar content in the upper part is relatively stable between 15% ~ 20%, and the potash feldspar is absolutely dominant, while the feldspar content in the lower part suddenly drops to 1% ~ 5%. The composition of cuttings is mainly quartzite and phyllite, followed by intermediate-acid extrusive rocks and carbonate rocks, with a small amount of mudstone, sandstone and siliceous rocks, and the content of cuttings in the lower part increases in time. Gravel composition is similar to that of cuttings in the same layer, with gravel diameter ranging from 2 ~ 10 mm, sand grains classified as good-medium, and rounded to sub-edge-sub-circle, sub-circle-sub-edge, point-line and point contact. Intergranular cementation is mainly composed of calcite and pore cementation, and basement cementation is also common. Others contain a small amount of dolomite.
6. Chale-Yantak region
Cretaceous rocks in Quele and Yangtak areas are sub-lithic feldspathic sandstone, sub-feldspar lithic sandstone, feldspathic sandstone, feldspathic lithic sandstone and lithic sandstone. The grain composition of reservoir rocks is mainly timely, accounting for 52% of the total grain size. Followed by feldspar, with an average content of 35%, including orthoclase 20% and plagioclase15%; The composition of cuttings is complex, mainly siliceous rocks, argillaceous rocks, tuff, rhyolite and mica schist, with occasional granite and andesite. The wave attenuation is obvious in time, the inclusions are well developed, and some of them have secondary enlargement in time. Feldspar has moderate to mild clayey or sericitization. The rock is dominated by fine-grained, coarse-grained-fine-grained sandy structure with micro-bedding; Particle support, good cementation type, mainly contact-pore cementation; Particle sorting-well, grinding circle is sub-edge-sub-circle, and particles are in point floating contact; The degree of cementation is loose, and the impurities in the interstitial materials are mainly argillaceous and iron-stained argillaceous, and kaolinite is rare. Mud is distributed on the edge of particles in the form of thin film, and it is reddish brown when iron is dyed. The main cements in Quele-Yangtak area are calcite and iron calcite, followed by dolomite, anhydrite and analcite, with a small amount of pyrite. Clay minerals in cement are mainly linear irregular illite/montmorillonite mixed layer minerals, and some samples also contain a small amount of foliated chlorite and flaky illite. Other authigenic minerals mainly include heteromorphic-semi-authigenic carbonate minerals, authigenic time, dissolved halite and cluster gypsum, all of which appear in the form of filling.
7. Nanka-Yurgon structural belt
The main rock types of Cretaceous reservoirs in Nanka-Yuergun structural belt are subalpine lithic sandstone, feldspathic sandstone and lithic sandstone. The timely content of clastic components is 50% ~ 57%, with an average of 54.3%. The feldspar content is 14% ~ 26%, with an average of 21.1%; The content of cuttings is 19% ~ 33%, with an average of 24.6%. The total amount of interstitial materials is 8% ~ 29%, and the average value is 16. 1%. Among them, the argillaceous content is 2% ~ 8%, with an average of 3.8%; The content of analcime is below 65438 0% ~ 3%, with an average of 0.88%; Dolomite content is 1% ~ 3%, with an average of 2%; Calcite content is lower than1%~1.62%; The content of anhydrite is 2% ~ 25%, with an average of 7.85%.
8. Yingmaili structural belt
The main Cretaceous rocks in Yingmai 1, Yingmai 19 and Yingmai 28 wells are lithic sandstone and sub-lithic sandstone. The timely content of clastic components is 5 1% ~ 59%, with an average of 55.07%. The feldspar content is 17% ~ 2 1%, with an average of18.5%; The content of cuttings is 265438 0% ~ 29%, with an average of 26.65438 04%. The total amount of interstitial materials is 1% ~ 30%, with an average value of 18.57%. The argillaceous content is below 1% ~ 20%, with an average of 5.07%; The content of analcime is lower than 1% ~ 8%, with an average of1.6%; The content of dolomite is 1% ~ 10%, with an average of 4.2%; There is also a small amount of iron-containing calcite, the content of which is below 1% ~ 4%. Occasionally see anhydrite.
9. Tage structural belt in East Qiu Li.
The main types of Cretaceous reservoirs in Tage structural belt of East Qiu Li are lithic sandstone and subalpine lithic sandstone. The seasonal content is 40% ~ 8 1%, with an average of 56.9%. The feldspar content is 7% ~ 17%, with an average of 10.53%, mainly potassium feldspar; The total amount of cuttings is 12% ~ 52%, with an average of 32.4%, including 7.2% of sedimentary cuttings, 2 1.06% of metamorphic cuttings and 4. 18% of magmatic cuttings. The interstitial materials are mainly ankerite, iron mud and pyrite. The content of ankerite is 1% ~ 30%, with an average of 4. 17%. The content of iron mud is 1% ~ 10%, with an average of 2.88%; The pyrite content is 65438 0% ~ 35%, with an average of 9.38%. The particles are in point-line, line-point and point-floating contact (Figure 5- 13).
Fig. 5- 13 Paleogene-Cretaceous Rock Type Map of Well Qiu Dong 8.
10. Dongyaha, Tiergen and Luntai tectonic belts
Cretaceous rocks in Yaha, Tiergen and Luntai structural belts in the east are mainly secondary lithic feldspathic sandstone and lithic sandstone. According to the thin section data of Well Donghe 8, the timely content is 56%, the feldspar content is 22% and the cuttings content is 22%. The content of quartzite chips is high, reaching10%; Followed by pyroclastic rocks.