| Time-lapse seismic technology as one of the main methods for the development of seismic technology in recent years have made great progress. Shell (Shell) and British Petroleum (BP) had considered the application of time-lapse seismic technology may cause the recovery to improve by about15%. In this regard, some of the major service and oil companies have invested a considerable force.Many of the old oil fields in China has entered the later development stage, due to complex internal structure of terrestrial lacustrine clastic reservoirs, strong heterogeneity, rock internal fluid distribution and reservoir development of dynamic, complex, resulting in average oil recovery.There are a lot of residual oil. Liaohe Oilfield is China’s major heavy oil production base. Liaohe western depression ShuYi District began in1997with the vertical well cyclic steam stimulation, throughput10-12cycles, the degree of recovery of24%; encryption of horizontal wells in2007,"direct level" combination of SAGD, at this stage the region, there were over2000wells, from the vertical well has reached70m, a very high degree of reservoir development. With the continuous deepening of the SAGD production work, reservoir development is facing the following problems:①the remaining oil distribution unclear; the②steam chamber development is unclear;(3) GuanTao Formation reservoir top underwater channeling;③The interbeds impact SAGD steam diffusiony. To solve the above problems, the urgent need is to carrying out time-lapse seismic work in ShuYi District. In this paper, through carrying out time-lapse seismic acquisition project in the Liaohe Oilfield, the feasibility was studied, and the first time-lapse seismic data acquisition in ShuYi, the first study of the seismic data, the time-lapse VSP data processing applications realized description of the test area gas chamber shape. Twice acquisition, processing seismic data results to carry out "three" Changes in a timely manner lapse seismic data interpretation, the remaining oil distribution results and through the implementation of the program, for verification and evaluation.The core content of this article is to shift a feasibility study of Time-lapse seismic and field consistency of the repeatedly acquisition.In terms of time-lapse seismic technology, rock physics technology is the bridge to connect the seismic response and reservoir parameters (such as pressure, fluid saturation, etc.). It was noted that the actual time-lapse seismic response to changes in recent years is often greater than observed in the laboratory caused by the fluid and pressure changes in response to change. Also, from another point of view to analyze this phenomenon, such as forward of the reservoir model, found that when the reservoir thickness and tuning thickness similar changes are much greater than the speed of change. This is mainly because of the speed of change will lead to changes in the tuning location, and the frequency of earthquakes. Thus, when the two seismic response subtraction, the difference is relatively large. Therefore, when shifting the feasibility analysis of time-lapse seismic, we must consider the reservoir itself changes, as well as other parameters of the reservoir, such as thickness and earthquake frequency. Time-lapse seismic feasibility study take into account the rock physics, seismic data quality and reservoir information and conditions. Risk maps, divided into high, medium and low risk areas. In this paper, laboratory experiments:heavy oil core P, T and V dependencies. The longitudinal wave velocity and amplitude of Liaohe heavy oil sandstone, sensitive depend on temperature sensitively, this relationship is the physical basis for time-lapse seismic in the heavy oil blocks, it proves that Liaohe heavy oil blocks have lapse seismic geological conditions; forward model by computer analysis shows that with increasing temperature, the presence of heavy oil has a great influence on the amplitude of the longitudinal wave. And oil saturation higher the greater the impact on the amplitude, the stronger the effect on the energy absorption; through the establishment of the reservoir model description:1before and after the oil reservoir, the seismic wave field is obviously different, the steam chamber reflected wave and the diffraction wave showed after heating steam chamber;2, before and after the oil reservoir, seismic wave propagation in shallow consistent in the reservoir internal differences are significant, but the obvious difference of seismic records and the migration profile of the shot gathers. Pilot experiment, the reservoir conditions and collection characteristics, range characteristics of the gas chamber and the Liaohe western depression ShuYi, geological structure and reservoir analysis to prove the feasibility of time-lapse seismic in the area.The so-called time-lapse seismic consistency is the degree of consistency refers to the time-lapse seismic acquisition parameters twice. Consistency is the key technology of the time-lapse seismic. Time-lapse seismic is repeated three-dimensional seismic data for reservoir performance, reservoir characteristics in the oil field development process caused by changes in seismic amplitude anomaly, the frequency change and the reflection phase axis drag phenomena such as the identification mark, so the theory on requirements of two or even each3D seismic acquisition, various factors must be exactly the same, to ensure that the difference of the two data collection is caused by changes in reservoir characteristics. Affected by many factors but in the actual production can not be achieved exactly the same, there will be a variety of errors, and repeated acquisition of seismic data between the error is mainly caused by several reasons:the acquisition parameters, tides, the water table, environmentalnoise, changes in the physical environment, recording equipment, the different source types, near-surface speed and the impact of processing factors. In order to eliminate these differences, a consistent approach (a total of prestack constraints, constraints, frequency, phase, speed, residual statics, etc.) in addition to the approach taken in the subsequent data processing to improve the consistency of the information outside, the most important or made to ensure the consistency of the best collection in the pre-acquisition process. In this paper, the measurement of the factors motivating factor, the receiver factors, several aspects of the recording equipment, environmental noise and near-surface factors to ensure the consistency of the acquisition parameters.ShuYi shift District lapse seismic acquisition:ShuYi a heavy oil resource-rich target layer is relatively shallow, the oil layer is very thick, good porosity and permeability conditions, the implementation of last-lapse seismic geological foundation; Heavy oil sandstone, longitudinal wave velocity and amplitude of temperature and oil saturation is more sensitive response relationship, this relationship is the physical basis of time-lapse seismic; Show that the area is very suitable to carry out time-lapse seismic forward modeling and actual production; Oil Development of surface obstacles, noise and development in order to ensure the quality of seismic data (less seismic acquisition footprints, high-resolution, high signal to noise ratio, high securitytruth degrees), band-earthquake construction process should be to broaden the variety of noise suppression, the maximum increase signal to noise ratio, resolution, fidelity and consistency. |
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