论文部分内容阅读
总的说来,水平井的应用一直局限于高渗透率储集层以及煤层、石灰岩层和页岩层等非常规地层。相反,对于需要进行增产改造的致密砂岩气藏,应用水平井完井技术实现成功的几率很小。得克萨斯州北部和俄克拉何马州锅柄状地区的Cleveland砂层就是这种成功的实例之一。就在最近,一些应用水平井获得成功的实例出现在得克萨斯州东部和路易斯安那北部的Bossier砂层和Cotton Valley砂层。水平井钻井和完井的成本一般为邻近直井的2～4倍,但在理论上,水平井产量能达到邻近直井的3～5倍。较高的天然气价格使水平井具有良好的经济潜力(Mulder等人,1992)。然而,实际研究结果表明,许多水平井的产量一般只比邻近直井多10%～30%。由于成本要比邻近直井高出2倍以上,因此水平井的经济效益显然不甚理想。本文讨论了水平井在致密砂岩气藏中进行设计、钻井和完井时,通过识别和控制风险提高成功率的方法。实践表明,采用简化的或按部就班的方法通常在下述完井环境中不发挥作用。岩性多样性和是否含油气性的情况需要通过适当的应用综合钻井和完井技术识别并控制。为获得成功,对于不同地质情况需要采用不同的钻井和完井技术。简单的说,要想获得再次成功别无他法。提出了致密砂岩气藏水平井钻井风险识别、认识及控制的详细方法。该方法考虑了水平井成功布井和完井所需考虑的所有复杂问题,包括气藏描述(动态和静态)、钻井设计、钻井施工、增产措施及生产。该方法也会对没有恰当的考虑这些问题将可能产生的后果进行举例说明。通过这种方法,能够确定水平井的可行性和经济效益。如果确定一口水平井经济可行,那么这种方法对致密砂岩气藏的开采和提高采收率的最佳完井方式(直井或水平井)的选择能够提供帮助。
In general, the use of horizontal wells has been limited to high-permeability reservoirs and unconventional formations such as coal, limestone and shale. On the contrary, for the tight sandstone gas reservoirs that need to be retrofitted with stimulation technology, the chance of success with horizontal well completion technology is very low. One example of this success is the Cleveland sand in the pan-handle areas of northern Texas and Oklahoma. More recently, some examples of successful horizontal wells have been found in the Bossier and Cotton Valley sands in eastern Texas and northern Louisiana. The cost of horizontal well drilling and completion is generally 2 to 4 times that of the adjacent vertical well, but theoretically, horizontal well production can reach 3 to 5 times that of the adjacent vertical well. Higher gas prices make horizontal wells have good economic potential (Mulder et al., 1992). However, the actual research results show that the production of many horizontal wells is generally only 10% to 30% more than the adjacent vertical wells. Because the cost is more than twice as high as the adjacent vertical well, the economic benefits of the horizontal well are obviously not very satisfactory. This article discusses ways to improve the success rate of horizontal wells by identifying and controlling risks while designing, drilling and completing wells in tight sandstone gas reservoirs. Practice shows that using a simplified or step-by-step approach usually does not work in the completion environment described below. Lithological diversity and hydrocarbon-rich conditions need to be identified and controlled through the proper application of integrated drilling and completion techniques. To be successful, different drilling and completion techniques are needed for different geological conditions. Simply put, there is no other way to succeed again. A detailed method of identifying, recognizing and controlling the risk of horizontal well drilling in tight sandstone gas reservoirs is proposed. The method takes into account all the complex issues that need to be considered for horizontal well completion and completion, including gas reservoir descriptions (dynamic and static), drilling design, drilling operations, stimulation measures and production. This approach also exemplifies the possible consequences of not properly considering these issues. By this method, the feasibility and economic benefits of horizontal wells can be determined. If a horizontal well is determined to be economically viable then this approach can assist in the selection of the best completion (tight or horizontal well) for the production of tight sandstone gas reservoirs and enhanced oil recovery.