低渗透油田超前注水合理技术参数优化研究

X区块FY油层为低渗透油藏,该区块采用超前注水的方法来提高原油采收率,运用数值计算和数值模拟的方法,在历史拟合的基础上对试验区超前注水参数进行了优化研究.对于合理注水强度,设计了5种注水强度方案,通过综合分析不同注入强度达到相同压力水平下的激动半径、储层压力分布和采收率,确定合理注入强度为1.65m~3/d·m;对于合理地层压力保持水平,设计了4种地层压力保持水平方案,并与同步注水进行比较,结果表明,当地层压力保持水平为原始地层压力115%左右时,试验区开发效果最好;对于超前注水合理投产时机,按所优选的注水强度配注各水井水量,设计了4个方案进行不同超前注水时间对比研究,结果表明,超前注水4～6个月,试验区开发效果最好.     

特高含水期井震结合注采系统挖潜调整研究

进入特高含水期后,开展注采系统调整挖潜剩余油是油田持续稳产的关键.为了提高特高含水阶段油田采收率,提出井震结合方法精细标定构造层位、认识储层特征,构建地质模型并数值模拟剩余油分布,针对剩余油应用井震结合解释成果设计注采系统调整方案并优化相应注水强度.实验区块研究结果表明:特高含水期,采用井震结合注采系统调整方法最终产油量和采收率分别提高31.21×10~4t和1.54%,能够达到有效挖潜剩余油的目的;而改变注水强度对最终开发效果影响显著,随着注水强度增加,采收率先增大后减小,存在最佳的注水强度为9m~3/d·m.     

非均质砂岩油藏异步周期注水数值模拟理论及应用研究

针对砂岩油藏周期注水特点,综合考虑弹性力、毛管力和重力的影响,建立起非均质砂岩油藏异步周期注水数学模型,并推导出相应的数值解.提出了一种新的流动系数取值方法,能够准确描述停注过程中毛管力作用引起的吸渗现象.在杏树岗油田周期注水试验区进行了实例验证,结果表明:地层压力相对误差为4.0%,产液量相对误差为3.2%,含水率绝对误差为0.9%.应用该方法对杏树岗油田厚油层不同周期注水方案进行了数值模拟计算,决定采取异步周期注水方案,并确定出合理的油层纵向组合方式和水井平面组合方式.平均注水强度为25m3/(d.m)左右,注水和停注半周期都是3个月.现场实施5个月后,区块综合含水率由92.17%下降到91.51%,产油量稳定,预计最终水驱采收率提高1%以上,取得了良好的开发效果.     

努拉里边底水油气藏提高采收率注采制度优化方法

开发边底水油气藏关键因素是抑制边底水锥进,延长油井无水采油期以提高油藏采收率,因此需要设置合理的开采速度和油水井注采制度.为深入了解不同井网系统和注采参数对边底水油气藏开发效果的影响程度,针对努拉里边底水油气藏开展研究.对边底水影响程度进行研究,得到各井在改变水体倍数后,以含水率差值4%为界限定义受边底水影响程度强弱,差值超过4%则定义为强水侵井,反之则为弱水侵井.在此基础上,采用油藏工程和数值模拟方法优选了注采参数,得出最优井距为1000m,最佳日注水量为30m³/d,最佳采液速度为4.75%-5%,并对优化参数进行了模拟预测,优化后累计产油量增加1.98×10⁴t,采收率达到54.7%.运用油藏工程方法对优化后的开发方式调整进行了分析,结果表明:可采储量采出程度小于62.78%时应以扩大波及体积为主,大于62.78%后应以增加驱油效率为主,目标区块优化后可采储量采出程度达到71.3%,相对潜力值i=0.81<1,处于开发后期,此时开发方式应以提高驱油效率为主.研究成果为同类边底水油气藏前期开发和后期措施调整提供了理论指导和借鉴.     

胜利断块油藏细分注水技术界限研究

老油田进入特高含水期后,剩余油分布更加零散,各种地质因素也因长期注水开发而发生了一定的改变.此时稳油控水难度进一步加大,为了进一步挖掘剩余油,控制含水上升速度、减缓产量递减,必须对注水井采取进一步的细分调整.基于水湿油藏注水井注水层段吸水效果,从注入水受力分析入手,运用达西定律推导出了水驱油藏水驱油全过程中的单位体积注入水沿竖直、地层两个方向运移的渗流速度公式,明晰了水驱油藏注水层段不同开发阶段砂岩吸水机理.研究结果表明,水驱油藏细分注水效果与岩石绝对渗透率、水相相对渗透率、注入水黏度、水动力压力梯度、注水井启动压力梯度、含水饱和度、地层倾角、油水密度差等参数有关.结合胜利油田断块油藏地质特征及细分注水工艺要求,制定了一套适合胜利油田不同断块区的细分注水技术政策界限:层段内渗透率变异系数小于0.3,砂岩条带宽度极比小于2.5,且东辛油区断块油藏层段内砂岩厚度小于6m,小层数小于4个;现河油区断块油藏层段内砂岩厚度小于5m,小层数小于5个;临盘油区断块油藏层段内砂岩厚度小于6m,小层数小于6个.矿场试验证实,该细分注水技术政策界限是合理、实用的,其为胜利断块油藏注上水、注够水、注好水,实现多层断块油藏的高效开发提供了技术保障,对类似油藏细分注水技术界限研究具有一定的借鉴意义.     

Study of the blow-up of solutions of systems of equations of hydrodynamic type

Mathematical Notes - We study the initial boundary-value problem for three-dimensional systems of equations of pseudoparabolic type. The system is similar to the Oskolkov system, but differs from...     

Distribution of types of symmetry of tensors of high degree

The asymptotic distribution of tensors of degree N in symmetry types is studied in this paper.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 155, pp. 181–186, 1986.     

Characterization of types of asymptotic discernibility of families of hypotheses

We give a characterization of the types of asymptotic discernibility of families of hypotheses in the case of hypothetical measures that are not, in general, mutually absolutely continuous. The case when the logarithm of the likelihood ratio admits an asymptotic expansion of the type of an expansion with local asymptotic normality is examined in detail. Examples are studied.Translated fromTeoriya Sluchainykh Protsessov, Vol. 15, pp. 64–71, 1987.     

Axiomatizability of reducts of algebras of relations

In this paper, we prove that any subreduct of the class of representable relation algebras whose similarity type includes intersection, relation composition and converse is a non-finitely axiomatizable quasivariety and that its equational theory is not finitely based. We show the same result for subreducts of the class of representable cylindric algebras of dimension at least three whose similarity types include intersection and cylindrifications. A similar result is proved for subreducts of the class of representable sequential algebras. Received October 7, 1998; accepted in final form September 10, 1999.     

Lengths of periods of continued fractions of square roots of integers

Empirical study of the period’s length T of the continued fractions of $\sqrt{Q}$ (for growing integers Q) shows several strange asymptotical results, for instance, $T\leq C\sqrt{Q}\ln{Q}$ . These results show important differences between the statistics of the elements of the continued fractions of random real numbers and of square roots of random integers.