中国东海气区初始产水评价图版的建立

Establishment of an initial water production evaluation chart for the gas province in the East China Sea

为了揭示东海盆地不同区域气藏气井初始产水特征存在差异的原因,以便于筛选有利的低渗透储层改造目标,应用气水两相毛细管压力及J函数定义式、幂函数型相渗模型、分流量方程,建立不同气柱高度下初始生产水气比的计算方法,再以东海气区标准毛细管压力、标准相渗实验数据为基础,计算并建立东海区域气藏不同气柱高度下初始生产水气比评价图版。在此基础上,由东海区域气藏已测试或投产井的数据对所建立的评价图版进行验证,并依据评价图版确定东海区域低渗透气藏适合储层改造的气藏物性条件。研究结果表明:①所建立的评价图版反映出各参数间的相关性与实际生产表现出的规律相似,且与实际数据匹配较好,验证了该图版建立方法及关键参数求取方法的正确性与可靠性;②以生产水气比小于1 m^3/10~4m^3作为筛选条件,东海盆地西次凹、中央隆起带及裙边的低渗透气藏(气柱高度一般在50 m左右)适合进行储层改造的储层渗透率应大于0.65 mD,中央隆起带中北部大型低渗透气藏(气柱高度一般大于100 m)适合储层改造的储层渗透率应大于0.26 mD;③在原位油气藏成藏条件下,气藏中不存在气水界面,所提出的方法及建立的评价图版则不适用。结论认为,所提出的初始产水评价图版建立及关键参数求取方法可以为国内其他气区的开发评价提供借鉴。

In order to reveal the reasons for the differences in initial water production characteristics of gas wells in different regions of the East China Sea Basin and to screen favorable targets for low permeability reservoir reconstruction,we established a calculation method of initial production water-gas ratios at different gas column heights by combining gas-water two-phase capillary pressure with J function definition,power function relative permeability model and fractional flow equation.Then based on the experimental data of standard capillary pressure and standard relative permeability in the gas province of the East China Sea,an evaluation chart on initial production water-gas ratio of the East China Sea at different gas column heights was calculated and established.Finally,the evaluation chart was validated by using the data of the tested or commissioned gas wells in the gas reservoirs of the East China Sea,and the physical property conditions suitable for reservoir reconstruction of low-permeability gas reservoirs in the area of the East China Sea were determined according to the evaluation chart.And the following research results were obtained.First,the evaluation chart established in this paper reflects that the correlation between the parameters is similar to the actual production law and matches well with the actual data,which verifies the correctness and reliability of the chart establishment method and the key parameter calculation method.Second,with the production water-gas ratio less than 1m^3/10^4m^3 as the screening condition,for the permeability of the low permeability gas reservoirs(with gas column height of about 50 m)in the west subsag,the central uplift belt and the periphery suitable for reservoir reconstruction shall be greater than 0.65 mD,and that of the large low permeability gas reservoirs(with a gas column height of more than 100m)in the north of central uplift belt shall be greater than 0.26 mD.Third,there is no gas-water contact in gas reservoirs under the hydrocarbon accumulation conditions of in-situ reservoirs,so the method and the evaluation chart proposed in this paper are not applicable.It is concluded that the method of establishing the initial water production evaluation chart and the method of calculating the key parameters proposed in this paper can provide meaningful reference for the development and evaluation of other gas fields in China.