savin1_20200909_104117論文igu2009docswgcfinal00587

1、DRILLING AND LOG DATA ANALYSIS OF GAS HYDRATE BEARING ZONE IN THEEAST SEA OF KOREAseoungsoo Park 1, Jeonghwan Lee 1, Seunghee An1, Sungrock Lee 2, Youngdoo Kim 11. R&D Division, Korea Gas Corporation2. Korea Gas Hydrate R&D OrganizationKeywords: 1.gas hydrate bearing zone; 2. seismic survey; 3. logg

2、ing interpretation; 4. LWD/MWD; 5.UlleungBasinAbstractGas hydrate is anticipated worldwide as a major future energy resource, due to its extensive deposits and environmentally friendly trait. Many countries such as U.S. and Japan have been conducting geophysical surveys and drillings through nationa

3、l science programs in order to investigate the distribution and resource quantities. In the case of South Korea, seismic surveys and drilling have been carried out from 2005 to 2007 in the Korean offshore to identify gas hydrate resources. This study classifies various gas hydrate bearing zones usin

4、g information acquired through analysis of LWD (Logging While Drilling) data obtained from the Ulleung Basin Area. Results from analyzing the acoustic velocity and resistivity log data show that gas hydrate bearing zone clearly exists. Porosity value have been computed using the data from density lo

5、g and sonic log and using the Archies Equation, gas hydrate saturation has been computed. Deducted saturations from two target areas,UBGH-09 and UBGH-10, are found to be 11.6% and 59.7% of the pore volumes respectively.1. IntroductionIn order to research and develop gas hydrate in the East Sea of Ko

6、rea, the Gas Hydrate Research and Development Organization of Korea (KGHDO) have been organized in the early 2005. It consists of Korea Gas Corporation (KOGAS), Korea National Oil Corporation (KNOC), and Korea Institute of Geoscience and Mineral Resources (KIGAM). The long term program was planned t

7、o be conducted for 10 years, consisting of three phases. During the first phase (2005-2007), KGHDO had conducted 2D seismic survey of its total 6,600 L-km to identify the potential area of gas hydrates in the Ulleung Basin area. And then the next year, 3D seismic surveys, such as multi-beam and grav

8、ity survey, was conducted throughout the approximate 400 of the prospect area (Fig. 1). From the interpretation of 2D and 3D seismic data, 5 points were selected for research drilling. Despite various researches conducted in the Ulleung Basin area, little is known about the initial formation and the

9、 transformation of the East Sea. However, it is generally considered that the East Sea started to form when the Northeast side of the sea expanded to form the Japan basin at the early Oligocene(around 32Ma),and subsea expansion occurred there at the latter Oligocene(around 18Ma) (Lee et al., 2007).F

10、ig. 1. Ulleung Basin in the east sea of Korea and 3D seismic survey area (Lee et al., 2007)Generally, the analyses of subsurface gas hydrate accumulations are conducted primarily through well logging interpretation and the observation of conventional or pressure cores along with seismic data. In 200

11、5, the Chevron Gulf of Mexico Joint Industry Project (JIP) demonstrated the ability to discern general trends of gas hydrate occurrence in the marine environment through advanced velocity analysis of existing 3D seismic data. Also in the early 2007, BPAX, the United States Geological Survey (USGS),

12、and others successfully drilled a research well to describe the accumulations of hydrate-bearing reservoir sand with drilling of Mt. Elbert prospect in the Milne Point region of the Alaska North Slope. For the first drilling of gas hydrates, we have adopted the LWD (Logging While Drilling) / MWD (Me

13、asurement While Drilling) technologies, and selected the GeoVISION-Sonic MD200 provided by Schlumberger, since it gathers high quality in-situ data of gas hydrate bearing formation conditions. The survey areas are located more than 185 km northeast of Pusan, South Korea, in water depths approximatel

14、y ranging from 1,356 m to 2,990 m. The field survey was conducted from the dynamically positioned multi-purpose offshore support vessel Rem Etive during 15th September through 15th November, 2007. TSMarine operated the drill ship, Fugro provided the drilling and coring, Geotek complemented onboard a

15、nalysis, and Schlumberger conducted the LWD/MWD. The total of 5 LWD downholes, 3 coring and 1 WL (Wireline Logging) were completed to final depths ranging approximately from 55.7 mbsf to 23.7 mbsf (below sea floor) and drilled to final penetrations ranging from 214.6 mbsf to 231.7 mbsf. The team had

16、 gathered both real time and memory type data, two of which showed little difference in value. The tools measured natural gamma, bulk density, neutron porosity, sonic velocity, formation resistivity and formation temperatureduring the drilling.2. ObjectivesGas hydrate has lattice structure formed by

17、 a special configuration of water and methane molecules. It is contained in both marine and permerfrost environment, usually along with sand or clay. It is importantwhether gas hydrate formation layer exists with sand or clay, because it is difficult to produce gas at imporous formation. Therefore,

18、the lithology of gas hydrate formation is more significant than the discovery of the massive gas hydrate formation. However, since the major purpose of the drilling was to investigate the existence of gas hydrate, it was carried out on the place most likely to contain gas hydrates according to the g

19、as hydrate indicator from the seismic analysis. We have used various elastic wave structures that will help verify gas hydrate reserves in the Ulleung basin. Out of the total of 5 drill sites, UBGH-01 and UBGH-04 are the ones situated on the western and southern quadrant respectively, and have the m

20、ost developed debris sedimentary with the most explicit BSR. UBGH-09 and UBGH-10 are the ones located near the center of the basin, and have highly developed turbidities sedimentary, and have the distinct characteristics of seismic chimney/vent/column formation (Fig. 2). Also, it has a very flat for

21、mation overall and shows a well-developed parallel formation structures when observed with the elastic wave (Lee et al., 2007). The selected area was the one that the acoustic blanking indicatorhas strongly suggested that the gas hydrate might exist.Fig. 2. Selection for the drilling sites from gas

22、hydrate indicator (Lee et al., 2007)The above two areas showed a difference in the LWD log as well. While the debris sedimentary area displayed no special interval in the log data, the turbidities sedimentary log data revealed comparatively high anomalies. Therefore the thesis will analyze the targe

23、t formation from UBGH-09 and UBGH-10 drilling locations to estimate the gas hydrate saturation. Hydrocarbon zones can be discovered using resistivity log tools, similar to the discovery of conventional oil and gas zones. Also, the acoustic wave of sonic logs can be used to find not only the litholog

24、y but also the gas hydrate zones (Jianchun Dai et al., 2008; M.W.Lee et al., 2008). Gamma ray log, density log and neutron log is useful in calculating the shale volume and porosities. To do this, we have extracted basic parameters such as formation temperature, formation water resistivity, mud weig

25、ht and drill bit size from the Well Report (SLB, 2007), and have inputted the data to IP 3.5 (Interactive Petrophysics from SLB), a professional log data analysis program. The thesis will first analyze the velocities of acoustic waves with respect to different depth, because this will allow us to di

26、fferentiate the gas formations and the gas hydrate bearing zones. Also, the results were compared with the gas hydrate formations P-wave velocities to show the accuracy.We intend to first analyze the lithology according to the drill sites natural gamma log, and to find thegas hydrate bearing zone an

27、d the porosity by observing to the resistivity log, in-situ density, neutron porosity and sonic velocity, and finally to calculate the gas hydrate saturation.3. Log dataThe drilling conducted from October 2007 to November 2007 was done so until it reached 20 - 30 m underneath the BSR, the DF(Drill F

28、loor) 3 m from the MSL (Mean Sea Level), and the water depth from 1600 m to 2102 m. The drilling was conducted at openholes using WBM. The inclination of the drill pipe was from 0 to 1.26 degrees, the azimuth was from 0 to 48.69 degrees, and the drill bit size was 21.59 cm. Borehole temperature was

29、6.0 degrees celsius, RPM 65, ROP 36.84 m/hr, mud resistivity 0.21 m, and the mud weight was 1.0g/ . The maximum resistivity values in certain wells can reach up to 170(m), and such massive intervals can be considered as bearing gas hydrate. However, since we cannot exclude the possible existence of

30、free gas, so we need to acoustic waves velocities with respect to different depth must be investigated to verify whether an interval is in fact a gas hydrate bearing zone. Fig. 3. shows the results acquired from P-wave velocity analysis in the formation from UBGH-01 to UBGH-10. At the UBGH-04, UBGH-

31、09, we can see the anomlis of velocity and UBGH-10 shows thelong term increasing of velocity about 133m intervals.Fig. 3. Acoustic velocities of each wellGenerally, in a pure methane hydrate zone, the acoustic wave velocity is known to be around 3,700m/s (Pearson et al., 1983; Sloan, 1990). As for t

32、he sonic velocity of this LWD drilling, from 1,400 m/s toBSRScale : 1 : 1200 UBGH-14DB:GH_LWD (5) DEPTH(0.M - 214.6M)07/12/200912:52DEPTH (M)DTBC (M/S)1300. 1800.50100150200Scale : 1 : 1200UBGH_10DB: GH_LWD (4)DEPTH(0.M-231.9M)07/12/200912:48DEPTH (M)DTBC (M/S)1300. 2300.50100150200Scale : 1 : 1200U

33、BGH-09DB: GH_LWD (3)DEPTH(0.M-227.5M)07/12/200912:50DEPTH (M)DTBC (M/S)1300. 2300.50100150200UBGH-04DEPTH (0.M - 223.5M)DEPTH (M)DTBC (M/S)1300. 1800.50100150200UBGH-01DB : GH_LWD (1) DEPTH (0.M - 218.2M) 07/12/2009 12:33DEPTH (M)DTBC (M/S)1300. 1800.501001502002,200 m/s has been recorded in the int

34、erval from UBGH-01 to UBGH-14. In detail, at UBGH-01, the P wave velocity was steady increased from around 1,450 m/s to 1,550 m/s as depth increasing. But at the UBGH-04, we can see the increasing of the sonic curve at the two points; the interval from 70 mbsf to 125 mbsf and near 150 mbsf. This dem

35、onstrates that the areas are likely to contain gas hydrates. Considering UBGH-09, the velocity increased up to 1,900 m/s and at UBGH-10 up to 2,150 m/s. This is a sufficent evidence of gas hydrates exitence. Because they approach towards 2,700 m/s(the velocityof pure gas hydrate saturation).Fig. 4.

36、Gamma ray curves, hole diameter curves, PEF(photoelectric absorption factor) curvesFig. 4 presents the shale volume and approximate lithology of the formation from gamma ray curve, hole diameter curve, photoelectri absorption factor. At UBGH-09, from the 130 mbsf, we can read an extensively sand-dom

37、inated interval, and at UBGH-10 all intervals is shale-dominated but we can read sand-veins. As for PEF, there are a few changes at the sandy inteval zone. All hole condition from the diameter curves have good qualities during drilling. By considering the acoustic velocities, hole diameter condition

38、, and the PEF curve values, we can avoid making an inaccurate conclusion by noting only one curve. The results of lithologies interpretation from its coring shows that mud, silt, sand and carbonate is well distributed (JJ Park, et al., 2008). So, it is necessary to compare and analyze allcurves to a

39、nalyze interpretaion of the log data.4. ResultsScale : 1 : 1200 UBGH-14DB: GH_LWD (5) DEPTH(0.M - 214.6M)07/11/200922:36DEPTH (M)GrC (GAPI)0. 150.VERD (IN)5. 20.PEF( - )0. 20.50100150200UBGH_10DEPTH (0.M - 231.9M)DEPTH (M)GrC (GAPI)0. 150.VERD (IN)5.20.PEF ()0. 20.50100150200UBGH-09DEPTH (0.M - 227.

40、5M)DEPTH (M)GrC (GAPI)0. 150.VERD (IN)5. 20.PEF ()0. 20.50100150200UBGH-04DEPTH (0.M - 223.5M)DEPTH (M)GrC (GAPI)0. 150.VERD (I N)5. 20.PEF ()0. 20.50100150200UBGH-01DEPTH (0.M - 218.2M)DEPTH (M)GrC (GAPI)0. 150.VERD (IN)0. 20.PEF ()0. 20.50100150200In order to classify and estimate a gas hydrate be

41、aring formation, we have interpretated LWD logdata and calculated porosity, water and gas saturation of the main boreholes using combined curves. So, we determined the properties of gas hydrate formation.Fig. 5. Gas hydrate bearing formation of UBGH-09, UBGH-10Fig. 5 shows gas hydrate bearing interv

42、als at UBGH-09 and UBGH-10. In this interval, to determin the gas hydrate saturation we was using the Archies Equation(1942). Actually, it may be difficult to apply the equation in a shale-dominated formation. However, in the Mallik 2L-38 gas hydrate estimation, Archies equation was used with conven

43、tional unconsolidated sands value of a=0.62, m=2.15, n=1.9386 (Collett et al, 1999b, Pearson et al., 1983). Also, Hacikoylu (2006) has estimated gas hydrate saturation using shaly sand values of a=1.65 and m=1.33, and unconsolidated sand values of a=0.62, m=2.15. Also, Jianchun Dai (2008) used value

44、s of a=0.90, m=1.90 and n=1.9386 to deduce gas hydrate saturation value in the deep sea of Gulf of Mexico and found about 30% gas hydrate saturation value near 300 mbsf. Therefore, it is appropriate to use GOMs parameter for the estimation of gas hydrate saturation as the dilling condition is simila

45、r to that of GOMs deep sea.Fig. 6 shows the interpretaion of LWD data at UBGH-09 and UBGH-10. At the results, we can see the yellow part in the fourth track. It is MOS(movable oil saturaton) and calculated from the water saturation ratio of invaded and uninvaded zone during drilling. In the case of

46、UBGH-09, its value was very low because it included many laminated shale formation. In UBGH-10, it had a comparatively more veiny type of porous matrix, it showed partial movability of dissociated gas. The second track shows porosity . Each total porosity of about 50% is shown. The third track indic

47、ates lithologies of the formation. Both UBGH-09 and UBGH-10 have various lithologies such as shale, silt, sand and limestone. At UBGH-09,it shows various shale types such as laminated shale, structural shale and dispersed shale until 125Scale:1:1200UBGH-09Scale : 1 : 1200 UBGH_10Scale: 1: 1200UBGH_1

48、0DB:GH_LWD(3)DEPTH(0.M-227.5M)2009-07-1321:01DB:GH_LWD (4)DEPTH(0.M-231.9M)2009-07-13 20:56Scale : 1 : 1200 UBGH-09DB : GH_LWD (4) DEPTH (0.M - 231.9M) 07/12/200912:48DEPTHVCLAV (Dec)RES_BD (OHMM)TNPH1 (dec)DEPTH VCLAV(Dec)RES_BD(OHMM)TNPH1(dec)DB: GH_LWD (3) DEPTH(0.M- 227.5M) 07/12/2009 12:50(M) 0

49、. 1. 0.2 2000. 1. 0.DEPTHDTBC(M/S)(M) 0. 1. 0.22000 1. 0.VCLSD (Dec)RES_BS (OHMM)PhiDen (Dec)(M) 1300. 2300.VCLSD(Dec)RES_BS(OHMM)PhiND(Dec)DEPTHDTBC(M/S)0. 1. 0.2 2000. 1. 0.0. 1. 0.2 2000. 1. 0.(M) 1300. 2300.50505050100100100100150150150150200200200200mbsf. However it is dominated by laminated sh

50、ale, so it does not affect the porosity but reduces thepermeability, and therefore is expected to disturb the flow of dissociated gas.Scale : 1 : 1200DB : GH_LWD (4)UBGH_10DEPTH (0.M - 231.9M)Scale : 1 : 1200DB : GH_LWD (3)UBGH-09DEPTH (0.M - 227.5M)2009-07-13 21:182009-07-13 21:24DEPTH (M)PHIT (Dec

51、)Vdisp (Dec)PHIT (Dec)DEPTH (M)PHIT (Dec)Vdisp (Dec)PHIT (Dec)0.6 0. 0. 1. 0.5 0.0.6 0. 0. 1. 0.5 0.PHIE(Dec)Vlam(Dec)BVWSXOT (Dec)PHIE(Dec)Vlam(Dec)BVWSXOT(Dec)0.5 0. 0. 1. 0.5 0.0.6 0. 0. 1. 0.5 0.Vstruc (Dec)BVWT(Dec)Vstruc (Dec)BVWT(Dec)0. 1. 0.5 0.0. 1. 0.5 0.PHIE (Dec)1. 0.VClay (dec)0. 1.VSan

52、d (dec)0. 1.VLime (dec)0. 1.VDol (dec)0. 1.PHIE (Dec)1. 0.VClay (dec)0. 1.VSand (dec)0. 1.VLime (dec)0. 1.VDol (dec)0. 1.5050100100150150200200Fig. 6. Properties & lithologies of gas hydrate bearing formation zone (UBGH-09, UBGH-10)At UBGH-09, it has been interpreted that from 129 mbsf to 151 mbsf,

53、there are substantial amount of sand and limestone. It has been estimated without the cutoff condition of shale volume, water saturation and porosity that it has an average total porosity of 51.4 %, that the average water saturation was about 48.8%, average shaly volume about 40.6%, and gas hydrate

54、saturation 11.6 % of pore volume. UBGH-10 has laminated shale-dominant interval from 9 mbsf to 149 mbsf, but in certain intervals it also showed thin sand and limestone. Ths intervals has been estimated with the same method and with average total porosity of 47.9%, average water saturation of about 14%,average shaly volume of 26