Complex Fault Block Reservoir Research Articles

Reservoir Characteristics and Three-dimensional Architectural Structure of a Complex Fault-block Reservoir, Beach Area, China

The objective area is a complex fault-block reservoir, and is provided by China Petroleum Engineering Design Competition(CPEDC). Reservoir characteristics, including stratigraphic features, vertical changes and section properties (thickness, percentage sand and percentage amalgamation) are documented. Based on comprehensive analysis on structural architecture and reservoir characteristics, a three-dimensional quantitative reservoir modeling is taken at a regional-scale of 69×97×37 m3 with the application of geostatistics as theoretical guidance, and thus high-resolution hierarchical reservoir model is generated with a combination of hierarchical data, structural data, physical data and well trajectory data. Therefore, the established three-dimensional geological model integrates all well-point information and structural information, and provides a basic model for subsequent sedimentary microfacies modeling and property modeling as well. Finally, three-dimensional fence diagrams, connecting-well sections and well group profiles are built successively.

New Progress and Challenges of Chemical Combination Flooding in China

Chemical combination flooding (CCF) is a greatly-enhanced-oil-recovery technique, which is developed on the basis of single chemical flooding such as polymer flooding, surfactant flooding, alkali flooding. The main types include AS, AP, SP and ASP. The mechanism of CCF is to make full use of different functions and synergy effect of various chemicals. Not only can it expand the macro swept volume by increasing the viscosity of the injection system, but also improve the micro displacement efficiency by reducing the interfacial tension between oil and water. Thus higher oil recovery can be gained. In China, fundamental research on CCF began in 1980’s. After more than 30 years’ indoor research and field tests, the technique has gone through four stages of development. At present, the mature technique is in the stage of industrialized application. Up to now, eight series of supporting techniques have been formed, 4 industrial tests of ASP combination flooding have improve oil recovery by 20%, and the ultimate recovery has been above 65%. Statistics show the cumulative oil production of all the CCF oilfield applications has exceeded 10 million tons. Remarkable development effect and economic benefit have been achieved. In China, CCF has become the dominant technique for greatly enhanced oil recovery after the used-to-be polymer flooding. At the same time, the field tests and application of CCF also exposed some problems and limitations, such as corrosion, scaling and output fluid emulsification caused by the existence of alkali, limited application in the relatively poor reservoirs with lower permeability, stronger heterogeneity, higher temperature and salinity. In the future, CCF technique will still face many challenges on its way of large scale applications in China. More emphasis will be put on the technical optimization and application’s expansion, namely from strong alkali-based ASP flooding to weak or no alkali-based ASP flooding, from high permeability reservoirs to reservoir with medium or low permeability reservoirs, from monolithic sandstone reservoirs to conglomerate or complex fault block reservoirs, from low temperature and low salinity reservoirs to high temperature and high salinity reservoirs. However, it is so exciting to see some new CCF techniques are booming now, such as alkali-free binary combination flooding and foam combination flooding etc. Some good expectations and results have been obtained in the laboratory research and pilot tests, showing broad application prospects and huge market potential.

Accurate Seismic Imaging Methods on Complex Fault Blocks of Subei Basin

Subei basin is well-known for its complex fault block reservoirs and has wide growth of shallow igneous rocks. These inherent geological characteristics seriously affect the accurate seismic imaging of target layers. Pre-stack depth migration is an effective imaging method for complex structure and velocity field zones. In order to verify nice imaging ability of Kirchhoff’s pre-stack depth migration (KPSDM) and reverse-time migration (RTM), imaging tests were carried out based on the velocity model for complex fault block of igneous area in Subei basin. Experimental results showed that under the condition of reliable high-frequency velocity field, RTM had obvious advantage in imaging of fault blocks, otherwise, KPSDM was a viable option. In order to verify above experimental results, by selecting seismic data with higher signal to noise ratio (SNR), a reliable high-frequency velocity field was established, and the imaging processing was carried out. The results showed that RTM has obvious advantage over KPSDM in the aspect of improving imaging results of fault blocks and target layers under igneous rocks. Therefore, the choosing of imaging methods for complex fault blocks with igneous zone depends on SNR of seismic data. If seismic data has high SNR, a more accurate high frequency velocity field can be set up. Thus RTM can achieve precise imaging for target layers. If the seismic data has low SNR, KPSDM will become a good choice. Key words: Subei basin; Complex fault block; Igneous rock; Velocity model; Reverse time migration

Artificial Gas Cap Flooding Technology of Complex Fault Block Reservoir

Complex fault block reservoir is a typical complex reservoir. Given the special structural characteristics and production technologies, develop level is very low. It is necessary to conduct the gas-flooding methods and technologies policies research. In this paper, based on structural characteristics, formation properties and development feathers, geological and numerical model were built, remaining oil distribution regularities and several influential factors were also analyzed. This research has a good meaning for Shengli Oil Field development.

Application of Three-Dimensional Fine Geological Modeling in Complex Fault-Block Reservoir with Low Permeability

Three dimensional geologic modeling is a powerful tool for reservoir development stages of geological study, it can solves many traditional problems existing in geological research through the establishment of precise three dimensional geologic modeling and represents an important direction for the further development of oilfield geological research. Low permeability and thin interbed reservoir of complex fault block have the characteristics of severe heterogeneity, complex relations of oil-water distribution, poor development effect, it is necessary to built high precision three dimensional geologic modeling in the process of oilfield exploration and to fine reservoir description and prediction on this basis, finally reach the purpose of reduce the risk of development and improve the economic benefit. This paper makes geological modeling research and builds structural models sedimentary micro-facies models and phased property model for Zhuzhuang block of Jiangsu oilfield by utilizing three dimensional geologic modeling technique and petrel geology modeling software on the basis of integrated using of geology, logging, oil production test, production of dynamic information, thus it provide a solid basis for reservoir's development and adjustment.

A Study on Development Adjustment Technique in the Block Bei301

In view of the broken fault, rapid sediment, high heterogeneity，high structural dip and rapid reservoir change in Block Bei301, fine reservoir description research was implemented including small fault identification, fan delta sedimentary microfacies subdivision and facies-constrained modeling, and the problems existing in production were analyzed zone by zone and interval by interval. Moreover, other unique adjustment strategies were implemented including reservoir engineering and numerical simulation researches, well pattern thickening, injection-production system adjustment, separated layer system adjustment, as well as horizontal well technology. Finally, oilfield development effect was improved and a series of unique adjustment technologies for complex fault block reservoir were preliminarily formed, which provides reference for the development adjustment in similar oilfields

Development techniques for deep complex fault block reservoirs with low permeability in Zhongyuan Oilfield

This article builds up the computational models of the minimum oil-bearing area, development investment, development profit, economic feasibility, decline rules, and economic reserve scale of deep low-permeability reservoirs. Study shows that the minimum oil-bearing area of the marginal reservoir is 0.02 km2; the economic threshold production is affected by reservoir burial depth, price of the crude oil, and operation cost of per ton of oil, of which burial depth and crude oil price are the sensitive factors affecting the economic production capacity; minimum reserve scale is affected by burial depth, recovery and consumption price of the crude oil and the operation cost of per ton of oil, of which burial depth and the consumption price of the crude oil are the sensitive factors affecting the economic reserve scale. Because of the increasing crude oil price, the original low efficiency or invalid reserves could be reestimated as the economic ones. The reservoir Es36–7 of the block Wei 360 is on the edge of the economic development.

Exploration strategies for complex fault block reservoirs in the Subei basin

The geological background of the Subei basin is that of small relief subsidence, low geothermal gradient, multi-sedimentary hiatuses, intense reconstruction of the basin, frequent magmatic activity, and a unique combination of source rock and reservoir. This geological background resulted in characteristics such as many small fault blocks, multiple oil-bearing formations, scattered oil distribution, mini- to small-sized reservoirs, and difficulties in exploration. Aimed at such characteristics, an effective exploration strategy was adopted, and the oil reserves, production and economic benefits of the Jiangsu oilfield were significantly increased. This exploration strategy included understanding the hydrocarbon generation mechanism of source rocks, progressive evaluation of oil resources, comprehensive research on the faulted systems, the distribution of oil reservoirs and their controlling factors. The techniques used included integration of acquisition, processing and interpretation with 3-D seismics as the core technology, trap description and evaluation, directional drilling and cluster drilling, integration of cuttings logging, gas chromatographic logging and geochemical logging, and integration of early reservoir description and progressive exploration and development. This strategy could be guidance for other complex fault blocks.