固井后环空气窜预测新方法

为了准确地预测固井后环空气窜的危险程度，有针对性地采取相应的防气窜水泥浆体系和工艺技术措施，利用7150型防气窜模拟实验装置研究了固井后环空气窜的影响因素。认为固井后环空气窜的主要原因是由于水泥浆失重引起的。分析了水泥浆静胶凝强度、失水等对水泥浆失重的影响规律，提出了新的固井后环空气窜预测新方法。给出了压稳系数GELFL的计算公式及评价标准：如果GELFL小于1，说明环空水泥浆液柱净压力在静胶凝强度达到240Pa时已不能压住地层压力，极易发生气窜，GELFL越小，发生气窜的可能性越大；如果GELFL大于1，说明环空水泥浆液柱净压力在静胶凝强度达到240Pa时可以压住地层压力．气窜危险程度较小，GELFL越大，发生气窜的可能性越小。现场应用该方法并配制相应的防窜水泥浆体系，有效地防止了环空气窜，主要油气层段水泥封固质量优良。

New predicating method of annular channeling after cementing

Channeling control cement slurry system and corresponding technology were used for predicating the damage degree of annular channeling after cementing and the influence factors to the channeling were studied by 7150 channeling simulator.It is considered that the main reason of leading to annular channeling after cementing is due to cement slurry weight loss.The law of static cementing strength and filter loss affecting the weight loss were analyzed and a new method was presented for predicating annular channeling.Calculatation expression and estimating criterions for determining GELFL were given: if GELFL is less than 1, gas channeling will easily occur because 240 Pa static cementing strength of annular cement pressure cannot overcome the formation pressure and the channeling possibility will increase with GELFL decreasing, but if GELFL is more than 1, all the above results will be contrary.The cement slurry system has been successfully used in field to effectively prevent annular channeling, while excellent cementing quality in the main reservoir has been obtained.