Fluid Detection in Tight Gas Sand from the Seismic Data

Transcription

1 Fluid Detection in Tight Ga Sand from the Seimic Data Jiang Ren, Zeng Qingcai, Ouyang Yonglin, Huang Jiaqiang, Heei, Hu Xinhai Reearch Intitute of Petroleum Exloration and Develoment-LangFang, Lang Fang of Hebei , China) Abtract: A the eimic attribute were affected by many factor at the ame time, uch a lithology, oroity, fluid roerty and o on, and different eimic attribute have different enitive ability to geology factor. In the roecting of lithology ga reervoir, it i very imortant to detect fluid with eimic data, o that we hould rioritize the eimic attribute which i more enitive to fluid. Thi aer i baed on examle of redicting tight ga reervoir, according to the exerimental data, and then rioritize the rock hyic model which i fit for tight and rock hyic modeling to aure the relationhi between the rock hyic arameter and lithology, oroity, ga aturation, and then filter bet eimic attribute which i mot enitive to fluid. From the reearch reult, Brie model i more uitable for tight ga and rock hyic modeling, it i feaible to detect the ga aturation in tight and, and the ga aturation can be redicted by the P+G attribute. Key word: tight and, rock hyic model, AO attribute, rioritizing eimic attribute, detection of fluid The technology of AO wa develoed and widely ued in the oil and ga roecting and reervoir decrition, by analyzing the feature of amlitude veru offet or angle to redict the lithology and ore fluid. Becaue the retack attribute were affected by the geology factor of lithology, oroity, fluid and o on, in the roect of lithology reervoir, it i very imortant to detect the fluid by eimic attribute directly, o it i the firt thing to otimize the mot enitive attribute to fluid, and then to redict the fluid by thi attribute. Bae on the rock hyic analyi, digging the law of elatic arameter affected by lithology, oroity and ga aturation, and then deduce the AO attribute affected by lithology, oroity and ga aturation, combining with forward modeling 1

2 1 Rock hyic analyi In order to clarify the rule how reervoir arameter affect the eimic reone, the firt thing wa building the link between the reervoir arameter and elatic arameter via rock hyic model. There are a lot of rock hyic model to aly to different condition, o the firt thing wa otimizing the model fitted for tight and by the calibration of lab data. The Xu-white model [1] wa alied widely in andtone modeling, it conclude 4 te, calculation of matrix elatic modulu, dry rock elatic modulu, mixed fluid elatic modulu, aturated rock elatic modulu. The calculation of mixed fluid elatic modulu will affect the calculation of effective rock modulu which affect the law of P-velocity and S-velocity. The model of Wood [] and Brie [3] were alied in the calculation of mixed fluid elatic modulu, each of them can be alicable only under ecial fluid ditribution attern, the Wood model will be alicable when fluid ditributed in homogeneou attern, the Brie model will be alicable when fluid ditributed in heterogeneou attern. Becaue oion ratio i a very imortant elatic arameter in the reearch of AO. Figure 1 how that the Brie model data can match better to lab data than Wood model data, and the lab data i meaured from the low oroity core whoe oroity i about 8%. It alo demontrate that oion ratio varied gradually with the ga aturation, different ga aturation ha different oion ratio. But Domenico [4] concluded that in unconolidated andtone, when the ga aturation get the 0%, the oion ratio will be lowet, even the ga aturation get higher, the oion ratio will kee a contant value, which imly AO only can detect whether there i ga in the ore, but can not redict whether it i indutrial ga reervoir. From thi reearch, the ga aturation can be detected by AO in tight and revoir.

3 试验数据点 Brie 模型 Wood 模型 Forward modeling analyi Fig. 1. Modeling data comared with lab data Baed on the rule of elatic arameter which are affected by oroity and ga aturation, beginning with the forward modeling which will hel to find the mot entive attribute, through the attribute analyi on the modeling data. The widely alicated attribute i P, G, P+G, P*G, fluid factor and o on. P and G i derived from Shuey [5] fomula, given by RPP = P+ G in θ 1) Where θ i the incident angle, P i intercet and the G i gradient, they are fitted by cd gather, the formula of each of the attribute i lited a bellow, 1 Δρ P = + ) ) ρ 1 Δρ G = ) 3) ρ P G + = 4) 1 Δρ P G = + ) 5) ρ 3

4 The fluid factor Δ F wa rooed by Catagna [6] in 1998, given by Δ F = b 6) Where ρ i the average -velocity, -velocity, denity of both ide of the medium, Δ Δ Δ ρ i the change of P-velocity, S-velocity, denity, b i the adjuting factor deended on the geology, b i gotten by the -velocity and -velocity fitting whoe data collected from the roject in thi cae. Pretack attribute are affected by fluid and oroity at the ame time, from the figure, the X axi i the oroity, the Y axi i the ga aturation, the color rereent the attribute value, by comaring, P+G can reflect the ga aturation, under the condition of higher oroity and ga aturation, it become larger accordingly. 3 Alication reuult Fig.. Two variable forward modeling analyi Figure 3 i the ga detection reult in the Sulige ga field with P+G, the high value of P+G rereent the higher ga aturation, the detection reult i conitent with the drilled reult. 4

5 Fig. 3. Ga detection reult by P+G 4 concluion Rock hyic analyi and forward modeling are the key technique of attribute otimizing, the rock hyic model otimizing i vital, it will affect the reult of attribute otimizing. In tight and reervoir, the Brie model i more uitable for rock hyic modeling. The mot enitive AO attribute are P+G which can detect the fluid directly. REFERENCES [1]Xu S, White R E. A new velocity model for clay-and mixture. Geohyical Proecting, 1995, 431): [] Wood AW. A Textbook of Sound, The MacMillan Co, New York, 1955: 360. [3] Brie A., Pamuri F, Marala A F, etc. Shear onic interretation in ga-bearing and. SPE Annual Technical Conference, 1995, [4]Domenico, S. Rock lithology and oroity determination from hear and comreional wave velocity, Geohyic, 498), [5] Shuey R T..A imlification of the Zoeritz equation. Geohyic.1985,504): [6] Catagna J P., Swan H W, Foter D J. Framework for AO gradient and intercet interretation.geohyic, 1998, 63,