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Study On Evaluation Method Of Water Trap Damage In Tight Sandstone Gas Reservoir

Posted on:2016-09-15Degree:MasterType:Thesis
Country:ChinaCandidate:F WangFull Text:PDF
GTID:2270330470453007Subject:Oil-Gas Well Engineering
Abstract/Summary:PDF Full Text Request
Tight sandstone gas is the priority research areas in the unconventional natural gas exploration and development, which plays more and more important role in reserves growth of natural gas and energy supply. Aqueous phase trapping induced by liquid phase invasion and retention is one of the most main formation damage types of tight sand gas reservoirs. The objective evaluation of aqueous phase trapping is the foundation for the prevention and cure of aqueous phase trapping, however, the previous evaluation methods on aqueous phase trapping foucs on relatively high permeability formation, whose application is limit in the evaluation of aqueous phase trapping in the tight sandstone gas reservoirs. It is essential to research the evaluation methods of aqueous phase trapping in tight sandstone gas reservoirs.The research objection of this dissertation is typical tight sandstone cores in the Ordos Basin. Based on influence factors and its mechanism of aqueous phase trapping, the governing factors of aqueous phase trapping in tight sandstone gas reservoirs are analyzed. The governing factors include the process of aqueous phase trapping in different operation form, physical properties and pore structure, initial water saturation, the slippage effect, formation sensitivity, which present the basement for the objective evaluation of aqueous phase trapping in tight sandstone gas reservoirs.Existing problems in the evaluation of aqueous phase trapping in tight sandstone gas reservoirs are analyzed by discussing the governing factors of aqueous phase trapping. The existing problems include salt-leaching of tight cores, establish initial water saturation, weaken slippage effect, stimulate gas reservoir pressure, characterize the process of aqueous phase trapping and discuss the index of aqueous phase trapping.The evaluation method of aqueous phase trapping in tight sandstone gas reservoirs including using repeated pressure salt-leaching method to leach salt in the tight sandstones, using the spontaneous imbibition method to establish water saturation, applying backpressure to the level of limit pressure to weaken the slippage effect, inflating cores to stimulate gas reservoir pressure, launching liquid phase invasion and displacement experiments to stimulate the process of aqueous phase trapping, evaluating the aqueous phase trapping by damage rate of permeability, rate of flowback and liquid flow rate is establishedBased the demand of evaluation of aqueous phase trapping, the apparatus for evaluating the aqueous phase trapping in tight sandstone gas reservoir is developed. And it can come true the process stimulation and evaluation of aqueous phase trapping in the nearly-balanced, over-balanced and under-balanced with high temperature and high pressure. The apparatus can monitor the liquid flow rate of cores in the process of nearly-balanced and over-balanced, and can monitor the gas phase volume flow rate in the process of under-balanced and the process of water displacement. The monitoring precision of liquid flow rate is0.001mL, the monitoring precision of gas phase volume flow rate is0.001mL/min.With the method of aqueous phase trapping and the apparatus, the operation instruction about evaluation of aqueous phase trapping in tight sandstone gas reservoirs is formulated. Taking the typical tight sandstone cores in the Daniudi gas reservoirs for example, the experiments for evaluating the aqueous phase trapping of Member He2, Member Hel, Member Shan2, Member Shanl and Member Tai2in the nearly-balanced, over-balanced and under-balanced conditions is conducted. Based the experiment results, the applicabilities of the evaluation method and the apparatus are verified, the microcosmic mechanism of aqueous phase trapping is analyzed from the view of water distribution, the influences from operation pressure and permeability to the aqueous phase trapping are discussed, the ideas of prevention and cure of aqueous phase trapping in tight sandstone gas reservoirs are presented from decrease liquid flow rate and flowback liquid timely and effectively. The operation instruction about evaluation of aqueous phase trapping can be used to evaluate the aqueous phase trapping in the tight reservoir and optimize working fluids in different operations, which guides prevention and cure of aqueous phase trapping in tight sandstone gas reservoirs.
Keywords/Search Tags:tight sandstone, gas reservoir, aqueous phase trapping, formation damage, evaluation method, evaluation apparatus
PDF Full Text Request
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