地層污損是指在鑽井、完井過程中，井眼周遭之油氣層因泥漿浸污的影響，使得滲透率降低之現象。泥漿浸污的污損機制可分為物理因素：由於井內泥漿壓力大於井外地層之壓力，使得泥漿流體中之固、液成份侵入地層孔隙，造成堵塞；以及化學因素：泥漿性質與地層流體之間的反應，如乳化作用，造成地層孔隙內流體性質的改變，使得流動能力下降。
在鑽井現場作業中，安全因素是第一優先考量，因此對於泥漿柱壓方面往往會遠高於地層壓力，使得泥漿容易因壓力差過大而入侵地層，此外由於泥漿比重的增加，其所含的固粒成份重晶石含量也會增高，使得入侵地層的泥漿會更容易堵塞孔隙，降低地層滲透率，造成地層污損。
本研究針對工程作業中可以掌控的技術方法及材料方法，進行降低地層污損之研究。在技術方法中，控制泥漿柱壓及地層壓力之間的壓力差，降低其所造成的影響。在材料方法中，研究使用低污損泥漿材料，來達到降低泥漿污損的效果。
本研究所得之主要結果及結論為：（1）地層滲透率降低程度約從26.2%變化至48.3%，當實驗的壓力差是從290 psi變化至1,016 psi時。（2）原始滲透率較低的砂岩較易受到實驗壓力差的影響，孔隙堵塞較為嚴重，泥漿反排不易。（3）過高的鑽井壓差設計，過高的重晶石使用量，都會使得地層浸污的程度變大。（4）地層壓力預測對於泥漿設計相當重要，生產井的地層壓力預測之正確性可以藉由前期探勘井的調查而有效的提高。（5）當要鑽過生產層時，建議使用改良型PHPA系統泥漿，其比Drilplex系統泥漿更有成本優勢。

The major results and conclusions from this study are: (1) the reduction on formation permeability is from 26.2% to 48.3% when the experimental pressure difference is from 290 psi to 1016 psi. (2) The low-permeability sandstone formation is more sensitive to the changes of the experimental pressure difference; the serious pore blockage is observed, and the invaded mud is hard to sweep. (3) A high mud weight design and a high amount of barite used in the mud system will make high formation damage. (4) The evaluation of formation pressure is a key factor to the mud system design; for a development well, the accuracy of the formation pressure evaluation can be increased by referencing the investigations of the exploration wells. (5) In engineering practice of low-damage mud using, the modified PHPA mud is better than the Drilplex mud because of the cost. The modified PHPA mud used in a drilling job for the production intervals is recommended.

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