在南阿尔及利亚油田的钻井和修井工作中,在井内密度较小的液体上面打密度大的水泥塞是一个比较麻烦的问题。当在远离造斜点或废弃井的井底打水泥塞时,要成功取得一个合格的水泥塞之前平均需要进行3次尝试。失败的水泥塞施工需要额外花费大概$75000,外加4天的钻井时间损失。对水泥塞的现场应用分析表明:导致水泥塞失败的根本原因是高黏段塞的流变性设计较差或根本没有设计造成的。事实上,直到最近高黏段塞的制作还是沿用以前的方法,并没有考虑水泥的特性以及水泥浆和高黏段塞之间界面的稳定性。密度大的液体下落到密度小的液体下面是一种自然趋势,只有阻止这种趋势,才能使远离井底的水泥塞保持静止状态直到水泥硬化。流体密度差越大或者井眼尺寸越大,水泥塞要保持稳定就越困难。为了提高稳定性,通常在水泥浆和钻井泥浆之间打高黏段塞。通过估算出的可靠的流体屈服应力,可以稳定不同密度的流体界面,这适用于任何尺寸井眼、井斜和流体密度差。当高黏段塞用于两个界面时可能出现不稳定:即在水泥浆与高黏段塞以及高黏段塞与钻井泥浆之间的界面。这些估算值已经转化成了计算机模型,用于高黏段塞和水泥浆物理性能的设计,这样界面的机械稳定性就能确保。这种计算机模型应用在南阿尔及利亚油田打水泥塞施工中,可以计算出流变性和密度的设计值,而水泥浆和高黏段塞中都将用到这两个值。实例研究表明,在最上面的水泥塞,其顶部的水泥正如期盼的那样。通过最近一系列的水泥塞施工,成功率已经从25%提高到接近100%。 In drilling and workover work in the southern Algerian field, it is troublesome to play a dense cement plug over less dense liquids in the well. When cementing plugs at the bottom of a well or away from incline wells, an average of three attempts are required before a successful cement plug can be successfully obtained. The failed cement plug construction costs an extra $ 75,000 plus a four-day loss of drilling time. The field application analysis of cement plugs shows that the root cause of failure of cement plugs is that the rheological design of high viscosity slug is poor or not designed at all. In fact, until recently the production of high-viscosity slugs continued with the previous method, without regard to the characteristics of the cement and the stability of the interface between the grout and the high-viscosity slug. It is a natural tendency for a denser liquid to fall below a less dense liquid, and stopping this trend will keep the cement plug away from the bottom of the well until the cement hardens. The greater the difference in fluid density or the greater the borehole size, the more difficult it is for the cement plug to remain stable. To improve stability, high-viscosity slugs are often struck between grout and drilling mud. By estimating reliable fluid yield stress, fluid interfaces of different densities can be stabilized, which is suitable for any size borehole, deviation and fluid density difference. Instability may occur when high viscosity slugs are used for both interfaces: the interface between grout and high-viscosity slug and high-viscosity slug and drilling mud. These estimates have been transformed into computer models for the design of high viscosity slugs and the physical properties of the grout so that the mechanical stability of the interface is ensured. This computer model is used in cement plug construction in the southern Algerian field to calculate the design values ​​for rheology and density, both of which are used in cement slurries and high-viscosity slugs. Case studies show that at the top of the cement plug, the cement at the top is as expected. Through the recent series of cement plug construction, the success rate has been increased from 25% to nearly 100%.