| JZ9-3 oilfield is a complex oil and gas reservoir,mainly composed of continental delta sediments,and the reservoir is highly heterogeneous,with a permeability variation coefficient of 0.72 to 0.95.The west zone of the oilfield is a binary combination flooding block,and it has entered the high water cut stage at present.Due to conditions such as large well spacing and large injection intensity of single well in the offshore oilfield,the interlayer contradiction between some formation is aggravated,and the injected fluid mostly flows along the high permeability belt and the high capacity channel,forming dominant seepage channels.In view of the above problems,the weak gel profile control and displacement technology is proposed in this paper,which can effectively improve the fluid entry profile,expand the swept volume of the medium and low permeability layer,and further improve the recovery after binary combination flooding.According to the gelation effect of weak gel system,the formula of weak gel system suitable for JZ9-3 oilfield is: 1750mg/L hydrophobic associating polymer AP-P4+30mg/L crosslinking agent chromium acetate,the gelling time is 48 hours,and the viscosity is about 2081.35 m Pa?s with a good stability.Taking the viscosity and gelling time as evaluation indexes,the main factors affecting the performance of the weak gel were studied,and the experimental results show that: the preparation water should be treated effectively to ensure that the water quality meets the standard before use;the gelling time is shortened and the gelling viscosity first increases and then decreases with the increase of temperature;when p H increases,the gelling time and the stability first increases and then decreases,and the optimal p H is 7~9;the shear action will reduce the initial gelling viscosity and the viscosity of the system gradually recovers with a good stability when the action is stopped.The performance of the weak gel system was evaluated by laboratory experiments,and the experimental results show that: the weak gel is a viscoelastic fluid,and the system is characterized by pseudoplastic fluid,dominated by elasticity after the gelation;the weak gel can be transported and migrated in the core,and the retention is more in the front half of the core;for cores with different permeability,the resistance coefficient and the residual resistance coefficient caused by weak gel are large,and the residual resistance coefficient is larger;the shunt rate of high permeability layer decreases significantly,while that of low permeability layer increases greatly after the injection of weak gel.A series of physical simulation experiments were carried out by using three cores parallel model to determine the injection parameters as follws: the optimal injection volume is 0.3PV,the injection timing is when comprehensive water cut reaches 70%,and the injection cycle is three cycles.The recovery of the weak gel displacement stage is 17.81%,the ultimate recovery is 71.62%,and the shunt rate of medium and low permeability layer increases from 12.90% to 39.88%.The indoor experiments have been carried out by using the designed row well pattern model,the results show that the weak gel can increase the producing degree of the medium and low permeability layer,and the remaining oil saturation will be further reduced.On the basis of the fine geological model of the target block,and the software Petrel RE is combined with,to carry out the numerical simulation.It is determined that the Formation I and III are the main remaining oil tapping formations and the distribution types of remaining oil in the plane are mainly imperfect well pattern,near fault and unidirectional effect.The numerical simulation results show that after the weak gel displacement technology is implemented in the target block,the oil production increases significantly,the comprehensive water cut decreases,and the cumulative oil increment of that stage is 72.08×104t. |
PDF Full Text Request