川西南部PLB气田栖霞组气藏开发潜力

Development potential of gas reservoirs of Qixia Formation,PLB gasfield,southwestern Sichuan Basin

为了进一步落实四川盆地西南部地区PLB构造下二叠统栖霞组气藏开发潜力,以PT1井为研究对象,分析了该气藏的地质特征、试采动态特征及稳产能力等。研究结果表明:(1)川西南部地区PLB构造栖霞组白云岩储层发育,孔隙度、渗透率关系显示具有双重渗流的特征,测井解释无水层,产出液分析结果认为PT1井产凝析水;(2)容积法计算结果显示,PLB构造栖霞组气藏天然气地质储量为81.13×10^(8)m^(3),地质储量丰度为3.08×10^(8)m^(3)/km^(2);(3)PT1井试采期间生产稳定,产能缓慢下降,试井结果显示远井储层物性较好,渗透率介于1.69~7.46 mD,近井区域渗流条件未发生明显变化;(4)采用3种方法计算PT1井栖霞组气藏动态储量介于(44.39~59.69)×10^(8)m^(3),预测PT1井在25×10^(4)m^(3)/d、34×10^(4)m^(3)/d、45×10^(4)m^(3)/d不同生产制度下的稳产时间分别为23年、15年、11年,在当前配产条件下,PT1井可以保持较长的稳产时间。结论认为:(1)PLB构造栖霞组气藏地质储量大,渗流条件好,具有较好的天然气勘探开发潜力;(2)PT1井试采期产量稳定,产少量凝析水,试井解释储层物性较好,具有较大的开发潜力;(3)根据不同方法计算得到的PT1井栖霞组气藏动态储量大,预测气藏稳产能力较强,展示了该区PLB构造栖霞组气藏良好的天然气开发潜力。

To further make clear the development potential of gas reservoirs of the Lower Permian Qixia Formation,PLB structure,western Sichuan Basin,PT1 well was taken as an objective to analyze reservoirs'geological features,production test dynamic characteristics and stable production.Results show that(i)Qixia Formation in this block is well developed with dolomite reservoirs whose porosity and permeability present a dual-seepage nature.Moreover,well-logging interpreta-tion holds that there is no aquifer,while the other analysis on output liquid deems condensed water produced in PT1 well;(ii)calculated from the volumetric method,Qixia gas reservoirs in PLB structure has OGIP of 81.13×10^(8) m^(3) and OGIP abundance of 3.08×10^(8) m^(3)/km^(2),respectively;(iii)the production is stable and the production capacity drops slowly during the production test.And this test reveals better physical properties far from PT1 well,for example the permeability be-tween 1.69 mD and 7.46 mD,and seepage conditions near the well do not change significantly;and(iv)after evaluated by three methods,dynamic reserves of Qixia Formation in this well are in the range of(44.3–59.69)×10^(8) m^(3),and it is pre-dicted that PT1 well will remain 23-a,15-a and 11-a stable production in the context of three production systems of 25×10^(4) m^(3)/d,34×10^(4) m^(3)/d and 45×10^(4) m^(3)/d.Especially,this well may keep longer stable production time under the current per-colation.In conclusion,Qixia gas reservoirs in PLB structure enjoy huge OGIP,superior seepage conditions,and great ex-ploration and development potential.What'more,during the production test of PT1 well,gas production is stable accompa-nying with a little condensate water.Its test interpretation suggests better physical properties and great development poten-tial.Additionally,some calculation endings from different methods display huge dynamic reserves in these gas reservoirs with stronger stable production capacity,indicating preferable development potential in Qixia gas reservoirs of the study ar-ea.