Abstract: While drilling horizontal wells having extended reach in the shallow reservoirs of Dongfang Gas Field in the Western South China Sea, challenges were encountered. They included balling-proneness in the shallow mudstone interval, lost circulation induced reservoir damage in the unconsolidated target layer, large frictional drag in RIH technical casing and narrow cementing pressure safety window. These factors contributed to the dual-risk of lost circulation and gas channeling. Combining with the previous regional operation experiences and optimizing the drilling fluid technical solution and compounding the pertinent additives, the first problem of debris balling in the shallow mudstone interval was solved, improved reservoir protection effect. Using floating coupling technology ensured smooth RIH of technical casing. After optimizing the mud column structure, the new cementing formula and casing centralization improved cementing quality. Key technologies for horizontal well of extended reach drilling in the shallow reservoirs of Dongfang Gas Field were developed. These technologies have achieved a good application effect during drilling the horizontal wells of extended reach in the shallow reservoirs of Dongfang Gas Field. No mud ball was formed during the shallow mudstone interval drilling of well DF-AH, and no lost circulation occurred in the target layer. The technical casing RIH was finished smoothly, and the completion/cleanup productivity was about 50% higher than the designed. Those key technologies have provided technical supports for the efficient development of gas fields.