阿姆河右岸区块地质特征与钻井设计

Geological characteristics and drilling design of the Amu Darya Right Bank Block,Turkmenistan

针对土库曼斯坦阿姆河右岸区块原钻探的190余口探井中,工程报废井40余口,干井、水井等地质报废井70余口,探井气井率仅占1/3的现状,正确认识阿姆河右岸地质特征,科学合理地钻井设计与钻井施工,提高钻井成功率和气井率,是阿姆河右岸项目需要突破的关键技术问题。在对卡洛夫组—牛津阶组气层储渗特征与几何形态特征研究的基础上,提出卡洛夫组—牛津阶组储层类型主要为堤礁相块状高孔渗储层、点礁相透镜状中—高孔渗储层和滩相层状中—低孔渗储层,应根据不同储层类型设计水平井、大斜度井和直井,以提高单井产能。并建议开展麦捷让等构造老井挖潜研究,筛选1～2口井进行修井、酸化或压裂等老井挖潜改造,获气可能性极大。新的钻井设计不能效仿原来部分井使用钻井液密度过大导致储层损害的做法,而应把该类不当做法视为勘探失败的教训,结合新的钻探成果认真地归纳、总结出符合该区地质特点的方法。

Among over 190 exploration wells previously drilled in the Amu Darya Right Bank Block,Turkmenistan,there are more than 40 and 70 abandoned for engineering and geological reasons respectively,so only one third are gas wells.In view of this,the key technical issues to be overcome for the Amu Darya Right Bank Project include full understanding of geological characteristics,scientific and reasonable design for drilling and construction,and improvement of drilling success rate and gas well rate.Based on the studies of gas reservoir permeability characteristics and geometry characteristics of the Callovian-Oxfordian Formation,this paper proposes the main reservoir types of the above-mentioned formation,including high porosity-permeability reservoirs appearing as lump barrier reefs,medium-high porosity-permeability reservoirs as lentoid patch reefs,and medium-low porosity-permeability reservoirs as layered beaches.In order to improve a single well's productivity,we should choose a design plan for a horizontal,high-angle deviated or straight well according to different types of reservoirs.It is recommended that more in-depth investigations be made into the potentialities of old wells in such structures like the Metejan Structure,and gas should be likely to achieve if 1 or 2 old well(s) are selected to be cleaned out,acidified or fractured.A new well design can not follow the former failure in some wells by using the drilling fluid with an over large density leading to a severe damage on the reservoirs.With the lessons from the former failed practices in exploration,we should,in light of new drilling results,carefully summarize and find out the drilling methods in line with the geological characteristics of the right bank of Amu Darya River.