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BACKGROUND The aim of this study was to investigate the significance of folate receptor-mediated staining solution (FRD) in examination of cervical lesions during gynecological examination. MATERIAL AND METHODS A total of 404 patients participated in this study. FRD staining was applied to screen high grade cervical lesions. ThinPrep cytology test (TCT) and human papillomavirus (HPV) testing were also used for screening high grade cervical lesions. Coincidence rate and KAPPA value of different methods were compared by SPSS software. RESULTS As for CIN2+ and CIN3+, sensitivities for HPV testing were (96.92% and 97.78%) >TCT classification 1 (90.77% and 91.11%) >FRD staining (80.00% and 86.67%) >TCT classification 2 (70.77% and 77.78%), respectively. While specificities for HPV testing were (7.08% and 6.44%)

Carbonate formations are usually highly fractured. The fractures exist at all length scales ranging from microscopic fissures to kilometer-size structures. Consequently, it is vitally important to rigorously characterize the multi-scale fracture system and to accurately model the fluid flow in such highly fractured porous media. In this paper, we will present an integrated workflow for characterization of natural fracture system and accurate numerical modeling of fluid flow in fractured rocks. The fracture characterization usually involves the integration of multiple data sources including core analysis, image logs and seismic interpretations etc., at different scales. The fracture mappings are thus required to perform at different length scales and resolutions. In this study, we present a systematic approach that characterizes the actual fracture distribution with seismic and log interpretations. Firstly, the small-scale fractures are interpreted using image logs and seismic anisotropy analysis with a co-Kriging and stochastic modeling approach. The small-scale fractures are initially constructed in an explicit fashion, and are then incorporated in the matrix medium using a flow-based upscaling procedure. Secondly, the large-scale fractures are mapped out from post-stack seismic data with ant-tracking and maximum curvature analysis. The reservoir is then gridded into unstructured tetrahedral or prism meshes to fully resolve these large fractures. This discrete fracture model (DFM) is employed in a reservoir simulation study based on such grid system. We applied the procedure for simulation study and history match on a portion of a carbonate gas reservoir in Longwangmiao formation in Southwest China. Currently, there are 7 horizontal and 2 vertical wells in operation. Due to the connection of some large-scale fractures to edge water, early water breakthrough and drastic water invasion were observed. We partitioned the reservoir block into 0.6 million cells, in which 153 large-scale and thousands of small-scale fractures are fully resolved. The simulation study was performed and automated history match was successfully achieved using our extended Ensemble Karman Filter algorithm based on a parameterized description of the fractures that are explicitly represented in DFM. This proposed overall procedure is able to efficiently capture such extreme flow dynamics and achieve significantly better history match results.

Based on cores, well logging and karstic paleogeomorphology, the identification method of multi-period paleokarstic water tables and their distribution and control on reservoirs were researched of Yingshan Formation in Tazhong Area, Tarim Basin. Three periods' water tables numbered 1 to 3 have been identified from bottom to top of Yingshan Formation in Tazhong Area. The corresponding typical horizontal undercurrent zones are characterized by single karst fabrics such as sack-like dissolved vugs or subhorizontal channels, combination of various karst fabrics like pre-existing high-angle fractures intersected by small caves and subhorizontal channels, and combination of multi-layered caves and different karst fabrics of large pores. On the plane, periodical rising sea levels caused the development of No.1, No.1 and 2, No.1, 2 and 3 water tables in karst depressions, slopes and highlands respectively. As the result of the nearly horizontal occurrence of Yingshan Formation, submembers of Yingshan Formation had tiny angles with fracture-cave bodies of each period's water table, so the karst reservoirs are characterized by “crossed strata regionally and developed along the stratum locally”. The distance between water table and unconformity, thickness of horizontal undercurrent zone and average thickness of reservoir all tended to increase with the rise of karst landforms. The karst highland and slope had 2-3 periods' water tables and thicker horizontal undercurrent zones, so they had thicker and better quality reservoirs, making them favorable exploration areas. Key words: paleokarstic water table identification, stages and distribution, reservoir-controlled pattern, Ordovician Yingshan Formation, Tazhong area, Tarim Basin

Based on the outcrop survey, 3D seismic data interpretation, drilling data analysis, the structural patterns and distribution of fault damage zones in carbonate strata of Tazhong Paleo-uplift were established to reveal the oil and gas enrichment law in the fault damage zones. The following findings were reached: (1) Through the filed survey, the fault damage zone system consists of fault core, damage zone with branch fault and fracture network. Affected by the active nature of the major faults, the fault damage zones differ in planar pattern and scale along the major faults. (2) 3D seismic profiles reveal that there are three types of fault damage zones in carbonate strata in Tazhong paleo-uplift, strike-slip fault damage zones, thrust fault damage zones and superimposed fault damage zones. Featuring 3 flowers and 3 root belts in vertical, the strike-slip fault damage zone can be subdivided into linear type, oblique type, feather type and horsetail type in plane. Thrust fault damage zones can be further divided into fault anticline type, anticline type and slope type. As the superimposition result of the above two kinds of fault damage zones, superimposed fault damage zones appear in three patterns, intersect type, encompassment type and penetrating type. (3) Cores from wells and geochemical data show oil and gas may migrate along the major fault and laterally. The feather type in strike-slip fault system, fault anticline type in thrust fault damage zone and intersect type in superimposed fault damage zone are possible sites for high production and efficiency wells. Key words: Tazhong Paleo-uplift, carbonate strata, fault damage zone, structural pattern, high production well area

Well tests for fractured vuggy carbonate gas reservoirs are challenging because of the diversity of well test curves, the ambiguity of interpretation results, and complexity of analysis models. In this section, the three-dimensional numerical well test analysis method and the lifecycle well test analysis method are presented. The multilayer, three-dimensional numerical well test model considers both lateral heterogeneity and vertical heterogeneity, and provides a mathematical description more similar to the actual reservoir performance. The combination of conventional analytical well tests, (2D and 3D), numerical well tests, and advanced production decline analysis can greatly improve the reliability of interpretation results and the forecasting accuracy of key development indices. Moreover, the application of well test analysis results in the gas reservoir description, and the cautions in performance monitoring, are explained.

Performance-based reserves can be estimated by the material balance method, rate transient analysis method, or well test method, among others. These methods can be combined depending on the characteristics of the gas reservoirs. For fractured-vuggy carbonate reservoirs, which are characterized by strong heterogeneity, complex fluid properties, multiphase flow in wellbore, production at variable pressure or variable rate, and poor quality of performance data; the traditional material balance method fails to estimate the single-well performance-based reserves. Therefore, a performance-based reserves estimation method integrating well test analysis and advanced production decline analysis is proposed. The new method can be used to effectively estimate the single-well performance-based reserves in fractured-vuggy gas reservoirs. The single-well performance-based reserves, recoverable reserves, and producing reserves estimation methods are illustrated with examples.

This chapter illustrates the connotation, status, role, and methodology of the dynamic description technique of gas reservoirs, and the problems in dynamic monitoring. The core of the single-well dynamic description is the evaluation of deliverability and stable productivity for the purpose of single-well production performance forecasting. The core task of gas reservoirs (clusters) dynamic description is the evaluation on effective reservoir distribution and performance forecasting of gas reservoirs (clusters). Dynamic monitoring and performance analysis are conducted throughout the process of gas reservoir development. The requirements for dynamic monitoring and performance analysis are different depending on the work objectives and tasks for the stages of gas reservoir development.

Compared to the widely distributed porous and fractured-porous carbonate reservoirs, the naturally fractured-vuggy carbonate reservoirs (NFVCRs) found in Tarim Basin, China, suffer from strong heterogeneity, multiple types of reservoir bodies, poor connectivity, complicated flow behavior and various water–oil interplay relationship in most cases. Due to lack of powerful and suitable EOR (enhanced oil recovery) strategies, depletion-drive recovery is commonly adopted for practical production, and the efficient oilfield development remains a great challenge to all of us. Understanding the relationship between reservoir bodies, configuration, water–oil interplay and depletion-drive performance, is essential to exchange of oilfield development scheme and further potential tapping of the remaining oil. By introducing an self-adaptive particle swarm optimization (DPSO) to tackle the shortcomings of the conventional fuzzy c-means (FCM) in terms of sensitivity to initial values, initialization with randomly generated clustering centers, and easy involvement in local minima, a novel integrated dynamic evaluation method for depletion-drive performance in NFVCRs based on DPSO–FCM clustering is developed. In this paper, different fractured-vuggy reservoir types are identified combing drilling & well logging response, numerical well test analysis and production test. The integrated diagnosis techniques including rate transient analysis, production decline analysis and reservoir energy evaluation, are employed to evaluate reservoir properties, furthermore, principal component analysis (PCA) is performed to reduce the dimensionality of input vector and establish the dynamic evaluation index system of depletion-drive performance. Taking a typical NFVCR in northern Tarim Basin as example, the proposed method is implemented to classify the production responses into four major patterns with eight sub-classes. Moreover, according to the insight of water–oil interplay relationship, depletion-drive production responses and identification of reservoir types, the water influx behaviors are divided into four general patterns. Eventually, the relevant dynamic clustering criterion and suitable potential-tapping strategies or measures are provided.

In this study, we propose an analysis method of gas injection development effect in the single well fractured-vuggy system. The fractured-vuggy reservoir has a complex spatial structure, oil-water relations and connectivity, of which single well fractured-vuggy system is a simpler model. Aiming at the problems of low recovery rate and production difficulties, based on the elasticity theory and fluid mechanics in porous, the elastic expansion energy and oil-water interface change before and after gas injection in the single well developing fractured-vuggy system are analyzed. And a theoretical mode of development effect after gas injection is built. Then an example analysis of Tarim Oilfield is conducted. The results show that: mining after repeated gas injection, water cut significantly decreased, yield and water free production increases gradually and the replacement rate increases with the gas injection. This shows that gas injection can effectively inhibit the rise of oil-water interface and improve the development effect of fractured-vuggy system.

Naturally fractured-caved carbonate reservoirs in China have some distinctive characteristics: deeply buried, multi-scale fractures, vugs and caves developed, strong heterogeneity, poor reservoir connectivity and no oil in matrix. Hydraulic fracturing is commonly used in order to connect offset fracture-cave system with wellbore and improve well performance for this kind of reservoirs, while how to properly evaluate hydraulic fracturing efficiency is still a major challenge. This paper presents an integrated evaluation method to solve this problem. The method mainly involves pressure transient analysis and rate transient analysis. Firstly, typical diagnostic curves of different fracture-cave patterns with and without hydraulic fracturing respectively are established through design analysis of numerical conceptual models. Then the curves are used for actual well stimulation and evaluation. Finally, reservoir properties of fracturing wells such as OOIP, hydraulic fracture properties, reservoir permeability, etc. are evaluated based on the integrated pressure transient analysis and rate transient analysis method. This new method has been applied to Tazhong No.I fractured-caved carbonate gas condensate reservoir in China. The reservoir's mid-depth is around 6000m and is currently under primary depletion development with an average annual production declining rate higher than 25%. Based on the understanding of seismic interpretation and geological study, 3 major reservoir patterns and 7 sub-patterns are classified. Then corresponding conceptual numerical models of these patterns with and without hydraulic fracturing are established, and typical diagnostic curves of pressure transient analysis and rate transient analysis for identification of these patterns are generated. And then, the results are applied to the actual well fracturing evaluation in Tazhong NO. I carbonate gas condensate reservoir. This systematic technique has been successfully applied to Tazhong No. I fractured-caved carbonate reservoir in Tarim Basin of China, which properly and correctly evaluates the properties of the hydraulic fracturing wells. It also provides a reliable method for decision making of hydraulic fracturing, which is helpful for effective and economic development of the reservoir.

Naturally fractured-vuggy carbonate gas condensate reservoirs in China have some distinctive characteristics: deep buried depth, multi-scale fractures, vugs and caves developed, poor reservoir connectivity and high production decline rate. It is hard to build effective geological models and run reservoir simulation for production forecasting. So how to properly forecast the performance of this kind of reservoirs is a major challenge. This paper presents a systematic technique of production forecast to solve this problem. The systematic technique mainly involves analytical and numerical production analysis (PA), analytical and numerical pressure transient analysis (PTA) and material balance analysis in combination with the geological analysis results. Firstly, using the analytical PA and PTA can quickly and correctly evaluate reservoir properties. Take Tazhong No.1 carbonate gas condensate reservoir in China for example to elaborate the details of this method. The results show that the systematic method can not only properly calculate the reservoir properties, but also can quickly and properly forecast reservoir performance of fractured vuggy carbonate gas condensate reservoirs. And the calibrated dynamic numerical model can both match well production history data and well pressure data. Examples are presented to show how these material balance analysis, analytical and numerical PA and PTA methods fully integrated and constrained with each other, and how the reliable results can be generated finally. Because of the poor connectivity characteristic of Tazhong No. 1 field, dynamic models for each fractured-caved unit should be built and applied for performance prediction.

Carbonate reservoir patterns play an important role in the production performance of oil and gas wells, and it is usually classified through static data analysis which cannot reflect the actual well performance. This paper takes the Tazhong No. 1 gas field in the Tarim Basin, China as an example to investigate the classification of carbonate reservoirs. The classification method mainly combines well test analysis with production analysis — especially the Blasingame type curve method. Based on the characteristics of type curves for well test analysis and the Blasingame method, the relationship between the type curves and reservoir pattern was established. More than 20 wells were analyzed and the reservoirs were classified into 3 major patterns with 7 sub-classes. Furthermore, the classification results were validated by dynamic performance analysis of wells in the Tazhong No.1 gas field. On the basis of the classification results, well stimulation (i.e. water flooding in a single well) was carried out in three volatile-oil wells, and the oil recovery increased by up to 20%.

The reservoir characterization and prediction of carbonate reef-flat complexes often have great difficulties because of the complexity of rock-fabrics and the rapid changes of carbonate depositional facies. This paper focuses on a carbonate reservoir in Tarim Basin, China. The dynamic behaviors between adjacent wells vary considerably although they belong to the same depositional facies, which indicates that the reservoir has strong heterogeneity. This paper proposes a new set of carbonate reservoir characterization in genetic units by integrating the geological, petrophysical and geophysical data. According to core-log interpretations, rock fabrics, pore types, reservoir properties, secondary porosity indexes have been acquired. The depositional cycles and key interfaces in stratigraphy sequence framework are determined. The relationships between the rock-fabrics, depositional cycles, reservoir properties, palaeo-weathering surfaces, responses of logs and seismic attributes have been studied, and reservoir genetic-unit models are constructed, which reveals that carbonate genetic units in different phases have specific rock-fabric associations and reservoir properties. The genetic units in different phases are delineated comprehensively in log and seismic data, and different reef-flat distributions are constructed. Finally, the seismic attribute relating to the secondary porosity indexes have been extracted in genetic-unit framework and it reveals the distribution of favorable reservoirs of carbonate reef-flat complexes. This paper reveals that different phases of genetic units of carbonate reef-flat complexes, as containing specific rock-fabric associations, crucial interfaces and fracture-vug development, thus key factors, control the distribution of favorable reservoirs. Phase I genetic unit, formed in relative sea-level rise, mostly with fine rock-fabric association of micrite calcarenite and micrite algae-bound limestones, are filling on the depressions, grooves or the flat area of carbonate platform, and its reservoir properties are very poor. Phase II genetic unit, with the tendency of upward- coarsening fabric association and top exposure surface, is overlaid on highlands along platform margin. Phase III genetic unit, composed of fracture-vug developed sparry gravel-bearing reef-skeletal limestones and sparry gravel- bearing calcarenites of reef-flat complexes, is almost distributed in the platform margin and overlaid on tops and nearby of previous genetic units, which means that, shallow water is suitable to reef-building organism mass-production, but frequent exposures and weathering have made favorable reservoirs developed. Drillings have proved that almost all high-production wells are within the area of phase II and III genetic units. Furthermore, the distribution and complicated internal structure of favorable reservoirs have been revealed by log-calibrated seismic attribute extraction in the framework of phase II and III genetic units. This paper illustrates an integrated case study, which helps geologists and reservoir engineers to support the development of Central Tarim Basin. In addition, it offers a methodology for the research of other similar oilfields.

Abstract In the Tarim basin of northwest China, large karst caves filled with oil and water have been found in Ordovician carbonate formation at depths exceeding 6,000 m. Sudden "bit drops" exceeding 10 m are not uncommon during drilling into such formation in the area, making logging data difficult to acquire. It is believed that wells drilled in the basin did not directly encounter with the caves but experienced high production are because of nearby caves. The well log data does not represent the productive reservoir. The relationship between reservoir properties and elastic parameters cannot be acquired from rock physics, reducing effectiveness of prestack inversion. The seismic reflection of karst caves is related to their size, shape, and content as well as the seismic signal to noisy ratio. Reservoir characterization using seismic techniques is a challenge. An innovative, integrated approach of four steps was taken to overcome this challenge. First, seismic reservoir interpretation from four levels of the target zone was performed based on the knowledge from drilling and the seismic data reprocessed with high fidelity and preserved amplitude. Then, seismic attributes were extracted along the interpreted horizons and the statistics of seismic attributes, which can represent the caves, were measured and evaluated. Next, well production was normalized for statistics on more than 20 production indicators (such as one-month, 6-month, and one-year oil equivalent). Finally, cross plots were made to find the relationship between seismic attributes with production indicators. Based on the results, fifty drilling targets were proposed and accepted by an operator. The integrated approach was verified based on drilling results. Introduction The study area is located in the west of the TaZhong area, Tarim basin, in China. Ordovician Karst reservoir is the target for oil exploration and production. Well-Driven-Seismic data reprocessing has improved the seismic images on caves and cave-fracture karst features. The seismic data used for the project has relative high fidelity. Prestack invertion was done using statistics wavelet as the sonic logs were not longer enough. The type of carbonate karst reservoirs is abundant, they consist mainly of tectonic fractures, diagenetic fractures, styloite, matrix porosity, dissolution porosity, and karst caves. Among them, the highly heterogeneous karst caves are the main resvervoir space for hydrocarbon accumulation. In seismic section, karst caves show as "a string of beads" (Figure 1), which is a vertical stack of positive amplitudes and negative amplitudes. From the seismic section we can see the length and magnitude of the strings of beads is different. This may be related to the cave size and shape. During the past few years, many studies including forward modeling have been carried out in Tarim basin. The relationship between the seismic attibutes and cave size, cave shape and content inside is complicated.