Eastern South China Sea LYD13 Oilfield Reservoir Dynamic Analysis

Chinese sea area is rich in oil resources,after offshore oil industry experienced more than 30 years of development,some of the old oilfield has entered ultra-high water cut stage,this stage is characterized by low oil production rate,large water production,more dispersed remaining oil and worse effect of meatures.In this paper,the eastern South China Sea oilfield LYD13 is taken as the example to have a thorough research on the offshore non-homogeneous bottom-water reservoir exploitation dynamic and distribution feature of the remaining oil.This paper,proceeding from the reservoir geological knowledge and utilizing the reservoir engineering methods to study the dynamic characteristics of oilfield development and analyze the impacting factors of oil-reservoir high recovery efficiency.Through geological modeling and numerical simulation study identify remaining oil distribution characteristics and laws,develop a reasonable developing technical countermeasures.This paper mainly achieved the following results and understanding:LYD13 oilfield's main productive layer,oil reservoir 25,is strongly non-homogeneous offshore block bottom-water reservoir,subordinate to littoral facies sediment,and its main geological characteristics are that interlayer developed with high clay content,the interlayers affected by sedimentary rhythm and microfacies are in homogeneously distributed lengthwise and crosswise,porosity-permeability condition of the reservoir changes in a wide range so that the difficulty of reservoir exploitation is increased.Analysis of the various stages of reservoir production shows that the exploitation goes quickly into the high-water stage,high water stage and ultra-high water stage are the main reservoir production period.Currently the majority of the reservoir is the ultra-high water wells.Single well liquid production is greatly different from each other,low oil production and fast rate of decreasing.Single well production decline is mainly harmonic decline and hyperbolic bias harmonic decline pattern,whole reservoir decline exponent is 0.65.After the measure of stabilizing-oil controlling water and adjusting exploiting layers in 2009,good results were achieved,the water cut and water cut rising rates have been controlled to a certain degree.Empirical formula and water-drive curve methods predict that the oil recovery efficiency is between 53% to 61%.After the adjustment of the exploiting layer in 2009,water-drive curve recovery prediction significantly increased and the ultimate recovery efficiency could reach up to 66% ~ 71%.Analysis shows that the influencing factors for the current high recovery-efficiency of 25 oil reservoir include that long-term water drive leads to reservoir parameters variation so that percolation condition becomes better,multiple batches of rolling development and stereo exploit potential remaining oil,dual-lateral wells and other new technologies enhance the single well oil production capacity.Using the imported Eclipse simulation software in oilfield for simulation,come to a conclusion that remaining oil distribution is mainly affected by two factors,geology and development.The remaining oil is mainly distributed in theL-1/3/5 sub layers of upper reservoir of 25 oil reservoir in length wise direction;Planar distributions are mainly located on the constructional high-profile sites,compact hypotonic layer shielding region,low-lying edge band,imperfect well pattern area and cross-well resident area in plumb-shaft concentrating part.Combined with the existing research results,for the reservoir characteristics,development status and potential distributions,three kinds of adjustment program are proposed to make predictions.According to the prediction results,under the current well network conditions,through increase frequency of electric submersible pump,to raising liquid 25%~30% can achieve better development results and economic benefits.