氣井水錐預測模式及堵水技術探討

臺灣的氣田多屬於水驅型氣田，而水驅型氣田在生産過程中，常因産率、氣水界面(Water Gas Contact , WGC)位置及地質條件等因素導致水錐(water Coning)發生。當氣水界面尚未達穿孔區間之底部，就引發伴産水，往往容易使生産井因液體聚積(Liquid Load Up)而提早停産，在水侵强度較强的氣田，此種現象更容易産生，因此有必要針對氣井建立水錐預測模式，由水錐預測模式决定氣井之臨界産率(Critical Rate)並提供生產層穿孔區問之訂定。上述做法僅是延遲出水時間，但當氣水界面持續上升，仍將導致出水而停産，此時生産井之儲氣層上方仍將殘留一段氣柱，以往須以鑽機進行修井工作，將生産層下段以水泥擠壓封堵，但此種作業所費不貲，因此必須進一步探討氣井之堵水技術，利用低成本且有效的堵水措施將水層隔開使生産井復産。本文首先蒐集文獻中常用之水錐預測模式，配合臺灣氣井之生産資料進行檢核，篩選出合適的水錐預測模式，接著以T氣田爲例探討氣井水錐出水機制與薄頁岩層阻隔作用，配合過去堵水井之案例分析，提出低成本且有效的機械式堵水方式。本研究顯示適合於臺灣氣井之水錐預測模式以Schols模式及Trimble and DeRose模式較佳。在氣井堵水方面，最主要必須考量氣層地質條件，利用地層中薄頁岩層之天然阻隔作用，可提高堵水效率幷延長再出水時間。近年來中油公司引進以撓曲油管(Coiled Tubing)經油管下Posiset之技術，配合氣層地質條件將水層隔開使生産井復産，其費用約新台幣150~200萬元，已成功地應用於數口氣井上，未來現場單位適時採用此技術應可使氣井延長壽命，提高氣田之油氣採收率。

關鍵字

水錐；氣水界面；液體聚積

並列摘要

Water coning is one of the phenomena often found in Taiwan gas wells, since most of them are water-driven reservoirs. The water rate will increase gradually even when the WGC still under the perforation interval if water coning happened. Finally, liquid load-up will kill the well especially for the highly water driven field. It is necessary to establish a prediction model to decide the gas critical rate and provide the information for perforation. The prediction method can only delay the time of water out, the well will cease production once the WGC is rise. The old workover method needs a drill rig to plug back the lower water zone with cement. Since the workover is expensive, a lower cost method should be found to reproduce the gas remained in the reservoir and block the water production. Several prediction models were reviewed in this study to find a suitable method with Taiwan gas wells production data. T gas field in Taiwan was chosen as a case study to identify the mechanism of water coning and block effect of thin shale formation, then proposed a lower cost and the most effective mechanical water shutoff method. Schols model and Trimble and DeRose model were selected as two suitable prediction methods for Taiwan gas fields in this study. It is important to recognize the geological condition in the formation when a water shutoff project was considered. We found, to utilize the thin shale formation as a water obstructer can increase the efficiency of water shutoff and delay the time of water out. Coiled tubing combine with Posiset techniques, cost NT$1,500,000-2,000,000, were used in CPC recently to reproduce the gas wells. Several wells were applied successfully. It is anticipated that employ this technique properly can extend the well life and increase the gas recovery rate in the future.

並列關鍵字

Water Coning ； Water Gas Contact (WGC) ； Liquid Load-up

國際替代計量

氣井水錐預測模式及堵水技術探討

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