Reevaluation Of Differential Gas Wells In The Second Gas Field Of Xinchang Gas Field

Sha-2gas reservoir structure of Xinchang field is located in a gentle nose structure sweeping eastward through Xiaoquan anticline in middle West Sichuan. It is characterized by low west high east, and a gentle slope inclination, which is unsymmetrical distribution. The internal fractures are undeveloped and it can be divided into four sets of sand body (JS21, JS22, JS2, JS2). It has a delta sedimentary system, an underwater distributary channel, and the thickness of sand body there has a wide distribution range and stable. Reservoir rock has the densification, poor physical property, the average porosity of9.68%. The average permeability is0.16×10-3μm2, which belongs to the typical tight gas reservoir. The heterogeneity is medium to strong, the plane heterogeneity is weak to moderate, and the interlayer heterogeneity is weak. The original formation pressure is41-45MPa, pressure coefficient is1.71-2.05MPa/100m, which is belong to the characteristics of abnormal high pressure. The original formation temperature is60.5～71℃, geothermal gradients1.82-2.39℃/100m, which is belongs to the normal geothermal gradient. It is an abnormal tight constant volume confining dry gas reservoir controlled of lithologic trap.Aimed at374old producers, gas reservoir reviews and selections have carried out in Sha-2gas reservoir in Shaximiao formation. Some new technologies of logging interpretation evaluation, such as the drilling gas logging value correction and recovery method, gas logging interpretation chart, geologic evaluation index weight assessment, are established under the condition of overbalanced. It uses the gas logging interpretation chart evaluation and potential geological index weight evaluation to evaluate the potential of preliminary screening layer adjoining well logging data. And it provides the first batch of7exploration wells with the cumulative thickness of141.40m. And it puts forward the second batch potential7layers in6Wells with the total thickness of177.40m at the same time as a potential alternative potential layer.It reviews Sha-2gas reservoir of old wells, and uses the geological index evaluation chart to249poor layer of the gas reservoir for potential zone evaluation. The results shows that the potential layer thickness of3979.00m, vertical thickness of3629.99m. Among it the first kind of potential34layers, the thickness of751.05m, accounting for18.88%of the total thickness, the vertical thickness of673.89m, accounting for18.56%of the total thickness; the second kind of potential33layers, thickness of684.70m, accounting for17.21%of the total thickness,603.95m thick, accounting for16.64%of the total thickness; and the third kind of potential182layers, the thickness of2543.25m, accounting for63.91%of the total thickness, the vertical thickness of2352.15m, accounting for64.80%of the total thickness.It initially forms series of old well reviews and evaluations technologies in Sha-2poor gas(gas-bearing) reservoir in Xinchang gas field, such as the drilling fluid density and gas shows correlation evaluation, the recovery and evaluation of overbalanced drilling gas logging correction, the interpretation and evaluation of the gas measurement chart, and the comprehensive geological index weight evaluation.