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Study And Prediction On Seismic Response Model Of Tight Reservoirs In Tabamiao Area, Ordos Basin

Posted on:2009-08-16Degree:DoctorType:Dissertation
Country:ChinaCandidate:J W YanFull Text:PDF
GTID:1100360242497818Subject:Energy Geological Engineering
Abstract/Summary:PDF Full Text Request
Tabamiao area of Ordos basin is one of the key exploration blocks of SINOPEC. The exploration of the area got breakthrough in 2004. In 2005, the area began producing. Till to the end of 2006, a gas deliverability of 1.67 billion m~3 was built. The area is the mainly developed milled-large size gas field of SINOPEC, which is predicted to get a gas deliverability of 3.24 billion m~3 till to the end of 2008.Three reservoirs are developed in the area, including Xiashihezi formation of Permian (gas formation of He1, He2, He3 member), Shanxi formation of Permian (gas formation of Shan1, Shan2 member) and Taiyuan formation (gas formation of Tai1, Tai2 member). The three reservoirs are overriding in longitudinal direction and folding in the plane, and constitutes compound accumulating bodies. The gas field is mainly compound gas pool of multi-folding gas formations. The sedimentary environment is from marine facies to transitional facies and continental river lake facies, with offshore facies in Taiyuan formation, delta plain subfacies in Shanxi formation and fluvial facies in lower Shihezi formation. The reservoir heterogeneity is strong. The interformational heterogeneity displays well-developed interbeds and weak vertical continuity. A series of sand bodies are composed of several cycles. Silt or mud interbedding usually exists between cycles, which cause weak continuity. The reservoirs are characterized by "low porosity, low permeability, and low pressure", which is the key problem for the breakthrough of exploration in the area.New progresses were achieved in the last fifty years, such as the fast developments of geological theories and seismic technologies, the new outcomes of geological cognitions, characteristics of gas pool, reservoir prediction technologies and drilling technologies, and the great breakthroughs of producing rate and high production accumulating formations. However, many difficulties rose, including layer classification and comparison, multi-well data conformity processing, high-precision reservoir prediction, pre-stack gas-bearing detection and reservoir parameters modeling during the development of gas field, which seriously restrict large-scale commercial development of natural gas in the area.The following results are achieved through the research.1. The logging interpretation model and gas-bearing interpretation standard of reservoirs were established, the lithology, physical properties and gas-bearing parameters were identified, the interpretation standard of gas-bearing lower limit. Well-seismic layer classification and comparison technology was proposed. The evaluation and classification criteria of reservoir were built; comprehensive evaluation and classification were carried out to reservoirs. The results of logging response characteristics analysis from different intervals show that the lithology is middle-sized grit with gravel in Tai2 member, Shan2 member, He1 member, Shan1 member, He2 member, He3 member and Tail member. The difference between sand velocity and mud velocity is not obvious, especially for gas-bearing sandstone, the sand velocity is agreed with or lower than mudstone velocity, which caused interpretation difficulty in reservoir prediction by using acoustic impedance properties.2. By using the method combined with seismic physical modeling and seismic numerical simulation, the seismic response rules and attribute characteristics of tight reservoirs in the area were identified, the recognition of seismic response characteristics of thin reservoirs were improved, and some criteria were provided for reservoir prediction and reservoir parameters modeling.3. Aiming at the characteristics of complex surface condition, large difference of S/N between original data and weak reflection energy of targets in the area, some measures were proposed to solve the processing difficulties (statics, de-noise, amplitude preservation processing, conformity processing and deconvolution processing). The chromatography statics processing technology was applied to solve the statics problem of long and short wavelength. Some de-noise technologies were used to attenuate noise and improve S/N of profiles, including pre-stack coherent noise attenuation in F-X domain, surface conformity anomalous amplitude pressing, self-adapt noise simulating rejection, anomalous seismic traces editing by statistics method and post-stack random noise attenuation. Surface conformity amplitude compensation and sphere diffusing compensation could well remove the impact of shooting and receiving factors on amplitude. Two times of surface conformity residual statics and velocity analysis improved the profile quality. The testing shows that combined application of surface conformity deconvolution and single- trace prediction deconvolution leads to high S/N profiles, and multi-traces impulse deconvolution leads to well wave group characteristics. The final processing result profiles have shallow, middle and deep wave groups with high S/N. characteristics of vertical and horizontal profiles are consistent. The main frequency of key targets is 30 Hz, and the optimal frequency zone is 8-70 Hz. The reflection characteristics of targets and special geologic bodies are clear. The aim of entire three-dimensional processing has been well realized, which provides data for following purpose processing and interpretation.4. Four types of AVO attributes parameters relevant analysis methods provide new approaches for gas-bearing prediction. Except for taking polarity inversion points in angle gather profile as gas-bearing marks, four types of gas-bearing recognition marks (four changing rules) are summarized, including faster decreasing energy of S-wave than P-wave, brighter gradient profile, stronger stacking wave energy of far trace than near trace, and larger Poisson ratio.5. Aiming at the characteristics of tight sand reservoir, ineffective recognition of sandstone and mudstone through wave impedance, two-step inversion separation technology was proposed. In the first step, profile reconstruction technology is applied to inverse the data reflecting the changes of lithology to distinguish sandstone and mudstone. In the second step, the properties and gas-bearing zone are discriminated based on the data. The recognition mark of sand formation and gas-bearing sand formation is established. The horizontal prediction pattern for Neopaleozoic reservoir in the north of Ordos basin was formed.6. Comprehensive evaluation and research were carried out in the area. The results show that the sand bodies of He2 member and He3 member are banding or moniliform distributed in SSE and SSW. The gas-bearing is poor, and the evaluation of the whole reservoirs is ordinary. Reservoirs in He1 member are widely distributed with large thickness and good gas-bearing zone, which can be regarded as one of the main reservoirs, as well as Shan2 member.Shan1 member is not as good the former two reservoirs and can be regarded as potential reservoir. Tai2 member absolutely is the main gas formation.
Keywords/Search Tags:Tabamiao area, logging response characteristics, seismic response characteristics, three-dimensional seismic data processing, seismic inversion, gas-bearing detection, reservoir evaluation
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