Fault Block Research Articles

Fine Depiction of the Single Sand Body and Connectivity Unit of a Deltaic Front Underwater Distributary Channel: Taking the Third Member of the Dongying Formation in the Cha71 Fault Block of the Chaheji Oilfield as an Example

By taking the third member of the Dongying Formation in the Cha71 fault block of the Chaheji oilfield as an example, the single sand body of the deltaic front underwater distributary channel is meticulously depicted by using the data of well logging and performance production. Portrays the vertical separation model, total lateral separation type, vertical type, lateral superposition type, 4 types of single sand body vertical superimposed and bay type, bank contact between docking, instead of four kinds of single sand body lateral contact type, and summarizes its logging facies identification. The quantitative prediction model of the single sand body was established, the characteristics of single sand body plane distribution were summarized, and the identification of the oil-water layer and the lower limit of reservoir effective thickness were studied. And we got the conclusion that based on the fine characterization of the single sand body and the lower limit standard of effective reservoir thickness, the distribution range of the effective reservoir and connecting unit is determined. Finally, the connectivity of the connecting unit is verified by dynamic data.

Analysis of reservoir-forming conditions of Beidong sub-sag in Beier Sag

Beier Sag is the main oil-rich sag in Hailar District basin. This paper analyzes the structure, source rock, relationship of source and reservoir, and deeply studies the reservoir-forming characteristics of Beidong sub-sag in Beier Sag. The study shows that the structure pattern of the bei-dong sub-sag in Beier Sag is characterized by “concave and uplifted interchangeably”, the present basin pattern is quite different from the prototype basin, develops northeast-east and north-east fault depressions in the Nantun formation during the sedimentary period. After three-stage tectonic transformation, it changes into the north-northeast direction, develops the palaeo-structure and has the geological conditions of reservoir formation. The dark mudstone of Nantun formation in Beidong sub-sag is thick, the abundance of organic matter is higher, and Type II is the main type; it is the medium-good source rocks with favorable conditions for reservoir formation. There are three sets of reservoir-forming assemblages in Beidong sub-sag, forming multi-type reservoirs. The succession of palaeo-structure is the main controlling factor of oil and gas accumulation, the favorable oil-bearing structures, such as reverse fault block and mid-concave uplift, are developed.

Syn-rift sedimentary evolution and hydrocarbon reservoir models in a graben rift sag, Songliao Basin, Northeast China

Identifying hydrocarbon reservoirs in lacustrine rift basins is a challenging task. This study uses seismic, well, and core data to analyse the sequence stratigraphy and describe the depositional systems and hydrocarbon reservoir models in the syn–rifted successions of Sujiatun sag in order to locate prospects in the Late Jurassic–Early Cretaceous continental rift basin. SQ2 is composed mainly of fan–delta and shallow lacustrine depositional systems. SQ3 and SQ4 consist of shallow lacustrine and semi–deep lacustrine depositional systems. SQ5 and SQ6 are composed of braid-delta and shallow lacustrine depositional systems, forming favourable reservoir sand bodies. Data obtained from thin section observation and physical property analysis show that the physical properties of braid-delta reservoirs are better than those of fan-delta reservoirs in terms of hydrocarbon accumulation. Geochemical analysis of the mudstones in SQ3 and SQ4 shows that they are excellent source rocks. Analysis of the conditions and characteristics under which the hydrocarbon reservoirs formed, indicate that Sujiatun sag models can be divided into six categories: a tilted fault–block hydrocarbon reservoir model, Syn trending fault–block hydrocarbon reservoir model, reverse trending fault hydrocarbon reservoir model, fault-lithologic hydrocarbon reservoir model, an updip pinch-out hydrocarbon reservoir model, and a lenticular lithologic hydrocarbon reservoir model. Research indicates that the distinctive depositional systems reflect three episodic syn–rifted stages. In particular, the rift climax influences the development of source rocks. Well-sorted sedimentary conditions and a large number of dissolution pores are key to improving a reservoir. The types and distribution of hydrocarbon reservoirs vary greatly over different structural stages and structural zones. Fault activity and a combination of different faults types, reservoirs, and source rocks jointly determine the enrichment degree of the hydrocarbon accumulation in different reservoirs. This study analyses the sedimentary evolution and hydrocarbon reservoirs within the syn–rifted successi to provide useful insight for oil and gas exploration in syn–rifted basins and may also be effective for use in areas in which wells or outcrop data are lacking.

Back analysis of a coastal cliff failure along the Forkastningsfjellet coastline, Svalbard: Implications for controlling and triggering factors

Based on a morphostructural analysis of a cliff coast segment of Forkastningsfjellet, back analysis of the August 12th, 2016 rock slide situated at 78°19′10”N/15°39′52″E was carried out. This rock slide comprises a volume of 175,000 m3, and indicates a partial reactivation at the front of the ~100 million m3 large postglacial Forkastningsfjellet rock slide. We studied the controlling and triggering factors of the reactivation using a 2-D limit-equilibrium calculations and a 3-D simulation with Scoops3D. Slope instability initiated along a pre-existing listric block fault that was inherited from the postglacial Forkastningsfjellet rock slide. The cause of the failure is attributed to a strength decrease and additional water pressures along the pre-existing sliding plane, possibly in combination with a degradation of the affected weak shales of the Rurikfjellet Formation, which build up a major part of the steep slope.Although the analysis suggests a structural control on the type and mechanism of slope failure, a significant impact of climate-related factors is inferred. Increasing temperatures and changing precipitation trends are reported from Svalbard. These are interpreted to foster permafrost degradation and reduce bonding forces in the thawing ice-filled fractures at the site. In addition, progressive weakening by more frequent frost and thaw cycles of the slaking shales and the introduction of additional water pressures to the rock mass are considered to contribute to the instability. The final trigger of the 2016 failure is attributed to a two-day rainfall that had preceded the event.The application of the Scoops3D software tool showed that it is capable of predicting the locations and affected volumes of landslides with reasonable accuracy, when the geological and structural setting is well established. Under such premises the tool can be used to support preliminary susceptibility assessments in study areas with comparable geological and morphostructural settings.

Jurassic stratigraphy of East Greenland

The East Greenland Rift Basin comprises a series of Jurassic subbasins with different crustal configurations, and somewhat different tectonic histories and styles. The roughly N–S elongated basin is exposed in central and northern East Greenland over a length of more than 600 km and a width of up to 250 km. The southernmost exposures are found in the largest subbasin in Jameson Land, while the northernmost exposures are on Store Koldewey and in Germania Land. The focus of the present revision is on the Jurassic, but the uppermost Triassic and lowermost Cretaceous successions are included as they are genetically related to the Jurassic succession. The whole succession forms an overall transgressive–regressive megacycle with the highest sea level and maximum transgression in the Kimmeridgian. The latest Triassic – Early Jurassic was a time of tectonic quiescence in East Greenland. Lower Jurassic deposits are up to about 950 m thick and are restricted to Jameson Land and a small down-faulted outlier in southernmost Liverpool Land. The Lower Jurassic succession forms an overall stratigraphic layer-cake package that records a shift from Rhaetian–Sinemurian fluvio-lacustrine to Pliensbachian – early Bajocian mainly shallow marine sedimentation. Onset of rifting in the late Bajocian resulted in complete reorganisation of basin configuration and drainage patterns, and the depositional basin expanded far towards the north. Post-lower Bajocian early-rift deposits are up to about 500–600 m thick and are exposed in Jameson Land, Liverpool Land, Milne Land, Traill Ø, Geographical Society Ø, Hold with Hope, Clavering Ø, Wollaston Forland, Kuhn Ø, Th. Thomsen Land, Hochstetter Forland, Store Koldewey and Germania Land. Upper Jurassic rift-climax strata reach thicknesses of several kilometres and are exposed in the same areas with the exception of Liverpool Land and Germania Land. In the southern part of the basin, the upper Bajocian – Kimmeridgian succession consists of stepwise backstepping units starting with shallow marine sandstones and ending with relatively deep marine mudstones in some places with sandy gravity-flow deposits and injectites. In the Jameson Land and Milne Land Subbasins, the uppermost Jurassic – lowermost Cretaceous (Volgian–Ryazanian) succession consists of forestepping stacked shelf-margin sandstone bodies with associated slope and basinal mudstones and mass-flow sandstones. North of Jameson Land, block-faulting and tilting began in the late Bajocian and culminated in the middle Volgian with formation of strongly tilted fault blocks, and the succession records continued stepwise deepening. In the Wollaston Forland – Kuhn Ø area, the Volgian is represented by a thick wedge of deep-water conglomerates and pebbly sandstones passing basinwards into mudstones deposited in fault-attached slope aprons and coalescent submarine fans. The lithostratigraphic scheme established mainly in the 1970s and early 1980s is here revised on the basis of work undertaken over subsequent years. The entire Jurassic succession, including the uppermost Triassic (Rhaetian) and lowermost Cretaceous (Ryazanian–Hauterivian), forms the Jameson Land Supergroup. The supergroup is subdivided into the Kap Stewart, Neill Klinter, Vardekløft, Hall Bredning, and Wollaston Forland Groups, which are subdivided into 25 formations and 48 members. Many of these are revised, and 3 new formations and 14 new members are introduced.

Three-Phase Fault Analysis on Transmission Line in Matlab Simulink

Now-a-days the demand of electricity or power areincreases day by day this results to transmits more power byIncreasing the transmission line capacity from one place to theother place. But during the transmission some faults areoccurred in the system, such as L-L fault (line to line), 1L-Gfault (single line to ground) and 2L-G fault (double line toground). These faults affect the power system equipmentswhich are connected to it. The main aim of this paper is tostudy or analysis of faults and also identifies the effect of thefault in transmission line along with bus system which isconnected to transmission line. Mainly the major faults in longtransmission lines is (L-G) single line to ground fault which areharmful to the electrical equipment. A proposed model intransmission line is simulated in MATLAB software to analysisand identified the faults. Fault block was taken from the sim-power system block library. The whole modeling andsimulation of different operating and different conditions offault on transmission line, their faults are L-G fault, 2L-Gfault, 3L-G fault and three line short circuit of the proposedwork is presented in this paper.

Deglaciation and neotectonics in SE Raasay, Scottish Inner Hebrides

Changes in the physical landscape of SE Raasay at the end of the last Quaternary glaciation are examined. The area is marked by a major fault system defining the Beinn na Leac Fault Block, and field survey shows this to comprise a rollover anticline in the SW, with extensional movement towards the NE along an oblique transfer fault, the Main Beinn na Leac Fault. The fault system was reactivated after the Last Glacial Maximum. Survey of a distinctive ridge of detached scree along the Main Beinn na Leac fault shows it to have involved a single movement of at least 7.12 m vertical displacement, arguably the greatest fault movement since before the Younger Dryas in Scotland. The present work confirms that the scree became detached during the Younger Dryas, but finds that it overlies a lacustrine deposit of at least 5.6 m of laminated sediments from a lake which had begun to accumulate earlier. Radiocarbon dating of peat overlying the lake sediments gave 10 176–10 315 cal years BP, but morphological and stratigraphical evidence indicates that drainage of the lake occurred earlier and only shortly before movement of the scree. Possible causes of displacement at the fault system are briefly discussed.

Post-ore change and preservation of the late Paleozoic Tuwu porphyry Cu deposit in Eastern Tianshan, NW China: Constraints from geology and apatite fission track thermochronology

The late Paleozoic Tuwu porphyry Cu deposit is located in the Dananhu–Tousuquan arc in Eastern Tianshan, northwest China. In this study, we present new apatite fission track data of the intermediate-felsic intrusions (i.e., diorite porphyry, tonalite porphyry, quartz porphyry, and quartz albite porphyry) from Tuwu, together with inverse thermal modeling and previous study, to reveal exhumation and cooling history. Apatite fission track length analyses indicate that the track annealing type belongs to a transition from the undisturbed basement distribution to the mixed distribution. As a whole, two phases of cooling were recognized from inverse thermal modeling including a protracted slow cooling period with an average cooling rate of 0.32 ℃/Ma during late Cretaceous to Miocene and moderate slow cooling with a cooling rate of 1.89 ℃/Ma from Miocene to the present day. The first phase of cooling can be mainly attributed to a tectonically quiet and arid to semiarid climate whereas the later phases of cooling related to structural activation occurred at ~25–15 Ma in response to a distant effect of the India-Eurasia convergence. In addition, the exhumation rates of Tuwu intrusions from the two stages are 10.7 m/Ma and 63 m/Ma, respectively. The calculated total exhumation thickness at Tuwu is 1.2–2.3 km since late Cretaceous. Based on the integration of stratigraphic sequence, tectonic setting, paleogeographic, geochronology, and low temperature thermochronology study, we suggest that the thick deposition of coal-bearing stratum during the early and middle Jurassic, the extended duration slow cooling and exhumation controlled by arid to semiarid climate, and the differential lifting movement of fault blocks are key factors for preservation of the early Carboniferous Tuwu Cu deposit.

A New MMC Sub-Module Topology with DC Fault Blocking Capability and Capacitor Voltage Self-Balancing Capability

A large number of modular multilevel converters (MMC) are connected to HVDC transmission systems nowadays. This paper aims at the short-circuit fault in the DC line of the HVDC transmission system and the problem of capacitor voltage imbalance in MMC, proposing a new type of MMC sub-module, which has both the DC fault self-clearing ability and the capacitor voltage self-balancing ability. This sub-module combines the topology of half bridge and full bridge. It uses the reverse capacitor voltage to forcibly turn off the conducting diode to block the fault current loop. At the same time, the two capacitances charge and discharge states are consistent by utilizing the operating mode of the sub-module. It is possible to directly achieve a self-balancing capacitor voltage without complex balancing voltage control. The MATLAB/Simulink simulation verifies the effectiveness of the DC fault blocking capability and capacitor voltage balance capability of the proposed sub-module.

3-D seismic interpretation of stratigraphic and structural features in the Upper Jurassic to Lower Cretaceous sequence of the Gullfaks Field, Norwegian North Sea: A case study of reservoir development

The 3-D seismic dataset is a key tool to analyze and understand the mechanism of structural and stratigraphic hydrocarbon (HC) trapping in the subsurface. Conventionally used subsurface seismic characterization methods for fractures are based on the theory of effective anisotropy medium. The aim of this work is to improve the structural images with dense sampling of 3-D survey to evaluate structural and stratigraphic models for reservoir development to predict reservoir quality. The present study of the Gullfaks Field, located in the Norwegian North Sea Gullfaks sector, identifies the shallowest structural elements. The steepness of westward structural dip decreases eastward during the Upper Jurassic to Lower Cretaceous deposition. Reservoir sands consist of the Middle Jurassic deltaic deposits and Lower Jurassic fluvial channel and delta plain deposits. Sediment supply steadily prevails on sea-level rise and the succession displays a regressive trend indicated by a good continuous stacking pattern. The key factor for the development of reservoirs in the Gullfaks Field is fault transmissibility with spatially distributed pressure. The majority of mapped faults with sand-to-sand contacts are non-sealing, which provide restriction for the HC flow between the fault blocks. The traps for HC accumulation occur between the post-rift and syn-rift strata, i.e. antiform set by extensional system, unconformity trap at the top of syn-deposition, and structural trap due to normal faults. Overall reservoir quality in the studied area is generally excellent with average 35% porosity and permeability in the Darcy range. Our findings are useful to better understand the development of siliciclastic reservoirs in similar geological settings worldwide.

Geophysical and hydrocarbon prospect evaluation of Nukhul Formation at Rabeh East oil field, Southern Gulf of Suez Basin, Egypt

Nukhul Formation is one of the primary oil reservoirs in the Gulf of Suez Basin. Rabeh East is an oil producer field located at the southern border of the Gulf of Suez. The present work deals with the geophysical investigation of Nukhul Formation in Rabeh East field using seismic lines and well log data of four wells, namely RE-8, RE-22, RE-25 and Nageh-1. The interpreted seismic profiles display that the RE-8 Well is the only well drilled within the up-thrown side of a significant horst fault block bounded by two normal faults. However, the other wells penetrated the downthrown side. The qualitative interpretation of the well logging data for RE-8 Well delineated two intervals have good petrophysical parameters and ability to store and produce oil. These zones locate between depths 5411.5 and 5424 ft (zone I) and between 5451 and 5459.5 ft (zone II). The calculated petrophysical parameters for zone I display water saturation (22–44%), shale volume (10–23%), total porosity (18–23%), effective porosity (12–20%) and bulk volume of water (0.04–0.06). Zone II exhibits water saturation (13–45%), shale volume (10–30%), total porosity (18–24%), effective porosity (11–20%) and bulk volume of water (0.03–0.05). This analysis reflects excellent petrophysical characteristics for the sandstones of Nukhul Formation in Rabeh East oil field for producing oil if the wells drilled in a suitable structural closure.

Geochemical Characteristics and Oil Source Correlation of Minfeng Area, Dongying Depression, China

The identification of the oil-source correlation plays a significant role in petroleum exploration and development. In this study, we identify the oil-source correlation by a hierarchical cluster analysis method combined with traditional methods. The results shed light on the oil-source correlation in Minfeng area and revealed the oil migration and accumulation process. The crude oil in different structural belts and different horizons has different geochemical characteristics. According to the four types of crude oil and their planner distribution, it was considered that the crude oil mainly migrates along with favorable sand bodies and unconformity surfaces in the lateral direction and then charged and accumulated in the glutenite of Sha3 and Sha4 members since the area from sag to Yan Jia Oil and the gas field was lacking of oil source faults. Further analysis shows that the traps of fault blocks in Yong’anzhen are formed in the same phase, while the crude oil generated in the early stage is charged and accumulated in the fault block of the near source. Along with increasing of the buried depth of source rocks, the overlying source rocks gradually entered into the hydrocarbon generation phase, when crude oil started to charge in the fault blocks farther away.

Research of Microbial-gel Combined Flooding Technology of Ba19 Block in Baolige Oilfield

Bal9 fault block is a medium-high temperature (58°C) reservoir in Baolige Oilfield. The crude oil is characterized by poor physical properties which has high wax and high gum content. The oil-water viscosity ratio is high and this leads to a low water flooding efficiency. The reservoir heterogeneity is high and the contradictions between layers are prominent. According to the characteristics of the oilfield, a microbial-gel combined flooding technology with the microbial flooding as the main body and the gel flooding as the auxiliary is developed to improve the overall development effect of the oilfield water flooding. Microorganism can improve the physical properties of crude oil, and appropriate gel flooding should be carried out to enlarge the sweep volume of microorganism work and improve the effect of microbial-gel combined flooding. By continuous application of this technology in Baolige Oilfield, the concentration of microorganisms is maintained at about 106 a/ml, and the whole microbial field is formed. The average annual reduction rate of crude oil is 48.1%. The microbial-gel combined flooding technology is verified to increase the recovery factor by 9.5%. Since the combined flooding was carried out in 2010, the recoverable reserves of the Ba19 block increased by 630,600 tons.

Optimization of horizontal well pattern in low permeability layered reservoir

The southern part of Jin45 fault block is a low permeability layered reservoir with thin oil layer thickness. And the development of horizontal well pattern has good economic benefit in Jin45 fault block. The oil layer distribution of reservoir is quite different. The distribution of main layer is stable, but the distribution of non-main layer is unstable. In this study, through reservoir engineering method and numerical simulation method, the horizontal well pattern direction, well pattern form, well spacing and horizontal well length are optimized to determine the horizontal well pattern of main layer. On this basis, according to the principle of “parallel deployment of horizontal wells and sharing injection-production well pattern”, the horizontal well pattern of non-main layer is preliminarily designed to ensure the development effect and economic benefit to the greatest extent.

Incorporating Persistent Scatterer Interferometry and Radon Anomaly to Understand the Anar Fault Mechanism and Observing New Evidence of Intensified Activity

Interferometric Synthetic Aperture Radar (InSAR) monitors surface change and displacement over a large area with millimeter-level precision and meter-level resolution. Anar fault, with a length of ~200 km, is located in central Iran. Recent seismological studies on the fault indicated that it is approaching the end of its seismic cycle. Although a large earthquake is imminent, the mechanism of the fault is not well understood. Therefore, understanding and discovering the mechanism of Anar fault remains a challenge. Here, we present an approach of displacement fault analysis utilizing a combination of InSAR data obtained from the persistent scatterer interferometry (PSI) method and 178 Sentinel-1 images (ascending and descending) (2017–2020). We incorporated groundwater samples from 40 wells, radon concentration anomaly mapping, Global Positioning System (GPS), and 3D displacement measurement acquired over four years (2016–2020). We investigated and monitored the deformation of the fault plate’s behavior over the last three years (2017–2020) to explore new evidence and signature of displacement. The results show that the time series analysis in the fault range has an increasing displacement rate in all dimensions. We observed that the line-of-sight (LOS) displacement rate varied from −15 mm to 5 mm per year. Our calculations show that the E–W, N–S, and vertical displacement rates of the fault blocks are 2 mm to −2 mm, 6 mm to −6 mm, and 2 mm to −4 mm per year, respectively. An anomaly map of the radon concentration shows that the complete alignment of the high concentration ranges with the fault strike and the radon concentration increased on average from 23.85 Bq/L to 25.30 Bq/L over these three years. Therefore, we predict rising the radon concentration is due to the increase in activity which resulted in a deformation. Finally, our findings show that the Anar fault is an oblique and right-lateral strike-slip with a normal component mechanism. We validated the proposed method and our results by comparing the GPS field data and PSI measurements. The root mean square error (RMSE) of the PSI measurement is estimated to be 0.142 mm. Based on the supporting evidence and signature, we conclude that the Anar fault activity increased between 2017 and 2020.

Source parameters of the 8 February 2016, Mw=4.2 Los Humeros earthquake by the inversion of InSAR-based ground deformation

We investigate ground movements induced by the 8 February 2016, Mw=4.2 earthquake at the Los Humeros Geothermal Field (Mexico) using Sentinel-1 radar interferometry. Previous estimated focal mechanism solution based on seismic data with a hypocentral depth of 1900 m could not resolve the measured coseismic surface deformation pattern. In this study, we applied inverse elastic dislocation models to estimate the source parameters of the seismic event. Our models suggest the reverse reactivation of the Los Humeros normal fault at a shallower depth (<1000 m), with a more significant left lateral component below ~400 m depth. The occurrence of such shallow events at Los Humeros pose increased risks for the neighboring communities and infrastructure. Therefore, continuous monitoring of seismicity and cautious planning of field operations are crucial.A NNW-SSE striking fault swarm, including the Los Humeros fault, acts as a major boundary of the subsiding area observed by InSAR time-series between February 2016 and May 2019. A potential explanation of the reverse reactivation of the Los Humeros fault and following downward movement of the eastern fault block is the depressurization of the whole hydrothermal system. Such depressurization can occur due to the exploitation of the geothermal field and/or due to natural pressure/temperature changes related to magmatic activity.

Origin and evolution of unconformities in a continental rift basin: a case study from the Lishu Depression in Songliao Basin, China

A variety of unconformity types are commonly developed during the rifting of a continental basin. Identifying their origin and evolution is a prerequisite to understanding the complex tectono-sedimentary evolution of the basin and to evaluate the basin’s oil and gas resources. Based on the 2D/3D seismic, geophysical logging, and subsurface lithological data, the unconformities within the rift layer of the Lishu Depression in the Songliao Basin are identified as disconformities, nonconformities, and four “types” of angular unconformities. Their evolution and origin are analyzed by associating the unconformities with the basin’s tectonic evolution. The results show that the rifting of the Lishu Depression was not a continuous process. Instead, several regional tectonic episodes influenced the basin’s evolution. Episodic compressional events and a phase of extension along the main faults determined the basin configuration and sedimentary fill characteristics of different sub-rifting stages. The tectonic history and related paleogeomorphology changes are the dominant factors in the formation of these different unconformity types. During the rifting process, the type and distribution of unconformity varied. In the initial rifting stage, the basin developed a nonconformity and four types of angular unconformities as the result of both regional uplift and fault block tilt. Rotation and tilting of the fault blocks during the intensive rifting resulted in two types of angular unconformities. Finally, in the recession rifting stage, a different form of angular unconformity and disconformity developed, mainly as a result of the regional uplift and subsequent subsidence.

Study on oil-water distribution law of Saertu reservoir in T66 block of Aogula oilfield

T66 block of Aogula Oilfield is a block structure area, in which faults are relatively developed, with different oil-water systems in different fault blocks, obvious oil-water interbedding phenomenon in longitudinal direction, no unified oil-water interface and complex oil-water distribution. In order to solve this problem, the oil-water layer identification and oil-water distribution law of reservoirs in this area are studied by using drilling data and resistivity correction model, and the oil-water interpretation chart is established. The analysis shows that the whole area is controlled by fault-structure, and the oil-water difference between the two sides of the fault is large, which is obviously blocked by the fault, and the fault cutting controls the oil-water distribution Local fault blocks are controlled by structure-lithology, and the whole reservoir of high fault blocks is well developed, showing the characteristics of high oil and low water, while the reservoir of low fault blocks is discontinuous, showing the characteristics of lithologic upward dip and pinchout and lens controlling oil and water.

Discussion on casing damage situation and prevention methods in a block

With the development of A oilfield and the constant adjustment of water injection scheme, affected by geological, engineering and development factors, the casing of oil and water wells will be damaged to varying degrees. Casing damage not only leads to the normal production of this well, but also needs to invest a lot of money for overhaul and renewal. At the same time, it will destroy the original injection-production system in this area and accelerate the production decline. Therefore, it is of great significance to study the causes of casing damage and its prevention technology for preventing casing damage and improving injection-production relationship. In this paper, a fault block in A oilfield is taken as the research object. By analyzing the present situation of casing damage in this block and the distribution law of casing damage wells in plane and longitudinal direction, combining with lithology and pressure conditions, the causes of casing damage are analyzed, and finally the countermeasures are put forward to improve the oilfield development effect and ensure the sustainable development of A oilfield.

Study on air foam flooding technology to enhance oil recovery of complex fault block reservoir by water injection

In order to solve the problem of rapid increase in water content and decrease in production after water flooding in fault block reservoirs, the air foam flooding experiments of static low temperature oxidation, single and double sand filled tube were carried out. The results showed that there was no absolute relationship between oxygen consumption and viscosity of crude oil, and there was a turning point of water saturation. The reaction rate is greatly affected by the reaction temperature. The displacement efficiency of single pipe is increased about 15%. The injection of air foam can effectively block the high permeable strip, and the middle low permeability layer is effectively utilized, and the recovery ratio is increased by about 10.9%. The plan of air foam flooding for Gao 16 block is compiled. The injection volume is 0.1PV and the gas-liquid ratio is 2:1. The recovery factor is increased by 5% and the cumulative oil increment is 22700 tons.