Research On Composite Plugging Technology For Heavy Oil Reservoirs

In the world the remaining recoverable reserves of heavy oil is very rich,so efficient ex-ploitation of heavy oil resource is one of the most effective ways to address the current shortage of oil resources.To achieve efficient development of the heavy oil reservoir,it is necessary to make a thorough investigation on the plugging removal technology for heavy oil reservoir to enhance oil recovery.In China the offshore heavy oil reservoirs mainly locate in Bohai region,where P oilfield is one of the most typical heavy oil field.So in this paper P oilfield is chosen as the research object.Based on the understanding of the reservoir characteristics,combined with the previous situation of earlier measures,a comprehensive study of P oil field' s heavy oil and oily sludge properties and plug removal technology are studied.The specific content of this paper is as follows:(1)The target reservoir is characterized as high porosity and porosity permeability with extremely strong heterogeneity and high content of clay minerals.The main causes of plugging in the region near the wellbore are heavy oil plugging,scale blockage,fine sand and mud clog-ging and the external fluid damage.In the process of exploitation,heavy oil is easy to wrap with scale,fine sand and external fluid then lead to the formation of oily sludge and other com-plex blockage,and as a result organic-inorganic composite blockage in oil well happens.So it is necessary to carry out the study focusing on how to relieve the multiple damages,and then improve the efficiency of viscosity reduction and plugging removal in the target reservoir.(2)Through the analyzing and summarizing the experience of pre-plugging removal measures,abandoning the conventional method that only uses a single acid,a new method,according to the thinking of "oily sludge dissolution,viscosity reduction,clogs dissolution",that strips organic blockages and inorganic ones as a breakthrough is proposed.,which focuses on the research on oily sludge treatment technology and heavy oil's viscosity reduction tech-nology.(3)By physical and chemical analysis method,the properties of heavy oil and oily sludge in P oil field is studied,including the relative density,viscosity,contents of water wax,four-component,the asphaltene molecular morphology,all of which provide a theoretical basis for the design research of suitable plugging removal system.(4)According to the properties of heavy oil and oily sludge in P oil field,making full use of the synergistic effects on organic extraction,emulsification and viscosity reduction,heat the gas self-generation,a new compound plugging removal system with self-generated thermal en-ergy and gas is developed,which is of highly security and efficient to plug removal.The new compound plugging removal system is made up of solvent system,heavy oil's viscosity reduc-tion system and self-generated heated and gas system.The system can effectively dissolve and strip the oil and organics from the oily surface,greatly reducing the viscosity of heavy oil.(5)An acidizing fluid formulation with efficient dissolution of inorganic blockage is opti-mized,which is aimed to relieve the inorganic damage and thus further improve the efficiency of the plugging removal.Core flooding experiment results show that,after the interaction be-tween the compound system and acidizing fluid formulation,the oily sludge's viscosity is re-duced after the reaction,viscosity-reducing and plugging removal effects have been greatly improved.(6)Based on the properties of the compound thermal chemical reaction system and exper-iment results of the dynamic core flooding and corresponding construction technique;the plug-ging removal technology suited for P oil field is formed.Field test results show that,the com-pound plugging removal technology can effectively solve the complex plugging problems in P oilfield.After the measure the liquid-producing capacity increases from 20.40m3/d to 86.41m3/d and oil production rate increases from 19.90m3/d to 70.48m3/d,which indicates the compound thermal chemical reaction system has remarkable performance on plugging removal and increasing oil production and can achieve good economic benefit.