劉占國(guó) 斯春松 壽建峰 倪 超 潘立銀 劉 群

(中國(guó)石油杭州地質(zhì)研究院 杭州 310023)

四川盆地川中地區(qū)中下侏羅統(tǒng)砂巖儲(chǔ)層異常致密成因機(jī)理

劉占國(guó) 斯春松 壽建峰 倪 超 潘立銀 劉 群

(中國(guó)石油杭州地質(zhì)研究院 杭州 310023)

四川盆地川中地區(qū)中下侏羅統(tǒng)砂巖儲(chǔ)層現(xiàn)今埋藏深度一般在1 500～3 000 m,但砂巖致密化程度異常偏高,其平均孔隙度小于5%,平均滲透率小于1 X10-3μm2,為典型的超低孔、超低滲儲(chǔ)層。巖石顯微鏡下成巖作用特征及壓實(shí)與膠結(jié)作用的減孔強(qiáng)度統(tǒng)計(jì)結(jié)果顯示,強(qiáng)壓實(shí)作用(包括壓溶作用)是導(dǎo)致砂巖儲(chǔ)層異常致密的主要原因。利用砂巖動(dòng)力成巖作用理論研究方法,通過(guò)對(duì)砂巖原始成巖物質(zhì)組構(gòu)及其所處的盆地成巖動(dòng)力學(xué)因素系統(tǒng)分析,進(jìn)一步討論了研究區(qū)中下侏羅統(tǒng)砂巖強(qiáng)壓實(shí)作用機(jī)理。認(rèn)為偏細(xì)粒度、高塑性巖屑含量為主導(dǎo)的砂巖原始成巖物質(zhì)組構(gòu)成為砂巖易于壓實(shí)的內(nèi)在因素;古深埋型埋藏成巖演化軌跡、較高古地溫場(chǎng)成巖環(huán)境以及油氣充注滯后的盆地成巖動(dòng)力學(xué)特征是砂巖壓實(shí)作用強(qiáng)烈的主要外因。

四川盆地 致密砂巖儲(chǔ)層 壓實(shí)作用 動(dòng)力成巖作用理論

川中地區(qū)中下侏羅統(tǒng)是四川盆地的唯一產(chǎn)油層系。隨著近年來(lái)研究區(qū)砂巖油田的發(fā)現(xiàn)和探明,且目前油田含油面積仍有不斷擴(kuò)大的趨勢(shì),使該區(qū)侏羅系砂巖油藏勘探成為又一重要勘探領(lǐng)域?？碧奖砻?中下侏羅統(tǒng)砂巖儲(chǔ)層現(xiàn)今埋藏深度普遍較淺,但砂巖致密化程度卻異常偏高,其孔隙度平均小于5%,滲透率小于1 X10-3μm2,為典型的超低孔、超低滲儲(chǔ)層;砂巖儲(chǔ)層的普遍異常致密導(dǎo)致了研究區(qū)呈“含油面積大”、但“油氣富集區(qū)難尋”的特點(diǎn),給砂巖油藏勘探帶來(lái)較大的困難和風(fēng)險(xiǎn)。因此,明確現(xiàn)今淺埋藏背景下砂巖致密成因機(jī)理是亟待解決的關(guān)鍵地質(zhì)問題,對(duì)研究區(qū)砂巖油藏勘探具重要意義,同時(shí)也具一定的理論意義。

1 地質(zhì)背景

川中地區(qū)位于四川盆地中部,大地構(gòu)造單元處于川中平緩構(gòu)造帶和川北坳陷低平構(gòu)造帶。區(qū)內(nèi)侏羅系地層厚度一般為2 500～3 500m,地層單元自下而上劃分為下統(tǒng)珍珠沖組(J1z)、東岳廟組(J1d)、馬鞍山組(J1m)和大安寨組(J1dn),中統(tǒng)涼高山組(J2l)、下沙溪廟組(J2x)和上沙溪廟組(J2sh),上統(tǒng)遂寧組(J3sn)和蓬萊鎮(zhèn)組(J3p),上侏羅統(tǒng)已大面積出露,中下侏羅統(tǒng)為油氣勘探的主要目的層系,可勘探面積達(dá)6 X104km2(圖1)。

研究區(qū)中下侏羅統(tǒng)含油砂巖儲(chǔ)層主要發(fā)育在下統(tǒng)珍珠沖組、中統(tǒng)涼高山組和下沙溪廟組。下統(tǒng)珍珠沖組地層厚度一般為150～250 m,儲(chǔ)層砂體主要發(fā)育在研究區(qū)西南部,單層厚度為3～15 m,砂體類型主要為多期三角洲平原-前緣水道砂體,巖石類型主要為巖屑石英砂巖;涼高山組地層厚度一般為150～500 m,儲(chǔ)集砂體主要發(fā)育在涼上段,砂體單層厚度普遍較薄,一般為2～6m,砂體類型以三角洲前緣水下分流河道、河口壩砂體為主,巖石類型主要為長(zhǎng)石巖屑砂巖,次為巖屑石英砂巖;下沙溪廟組地層厚度一般為200～400 m,儲(chǔ)集砂體相對(duì)最為發(fā)育,單層厚度可達(dá)8～21 m,砂體類型主要為三角洲分流河道、河口壩砂體,巖石類型主要為長(zhǎng)石巖屑砂巖和巖屑長(zhǎng)石砂巖。

2 砂巖異常致密主要成因分析

2.1 砂巖物性特征

根據(jù)研究區(qū)砂巖物性資料統(tǒng)計(jì)分析結(jié)果(圖2),下沙溪廟組砂巖孔隙度分布在0.7%～12.3%范圍內(nèi),平均4.2%,滲透率分布在0.001 X10-3～3.21 X 10-3μm2之間,平均0.21 X10-3μm2;涼高山組上段孔隙度分布在0.2%～10.2%范圍內(nèi),平均3.7%,滲透率分布在0.001 X 10-3～0.91 X 10-3μm2之間,平均0.11 X10-3μm2;珍珠沖組砂巖孔隙度分布在0.4% ～4.7%范圍內(nèi),平均2.4%;滲透率分布在0.001 X 10-3～0.81 X10-3μm2之間,平均0.11 X10-3μm2。總體上,中下侏羅統(tǒng)砂巖儲(chǔ)層普遍異常致密,孔隙度平均小于5%,滲透率小于1 X10-3μm2,為典型的超低孔、超低滲儲(chǔ)層。

2.2 砂巖異常致密成因

鑄體薄片鏡下微觀特征顯示,研究區(qū)中下侏羅統(tǒng)砂巖強(qiáng)烈壓實(shí)作用現(xiàn)象十分顯著,主要表現(xiàn)為砂巖原生孔顯孔罕見,粒間膠結(jié)物含量普遍較低,顆粒間呈線-凹凸、局部嵌合接觸。石英顆粒邊緣具明顯壓溶縫合現(xiàn)象,長(zhǎng)石顆粒雙晶壓彎、斷開,云母碎片壓實(shí)扭曲、錯(cuò)斷及塑性巖屑?jí)簩?shí)變形呈假雜基狀等(圖3)。

圖1 研究區(qū)地理位置及地質(zhì)概況簡(jiǎn)圖(Ⅰ-川西坳陷帶;Ⅱ-川北坳陷帶;Ⅲ-川中平緩構(gòu)造帶;Ⅳ-川南斷皺帶;Ⅴ-川東斷皺帶)Fig.1 Sketchmap showing the location of the study area and its geological context(Ⅰ-western depression zone;Ⅱ-Northern depression zone;Ⅲ-Central gentle structural zone;Ⅳ-Southern bruchfaltung zone;Ⅴ-Eastern bruchfaltung zone)

圖2 中下侏羅統(tǒng)砂巖孔隙度-滲透率分布Fig.2 Sandstone porosity and permeability distribution in Middle and Lower Jurassic

圖3 中下侏羅統(tǒng)砂巖強(qiáng)壓實(shí)作用顯微特征Fig.3 Photomicrographs showing the intensive compaction of sandstone in Middle and Lower Jurassic

為定量研究研究區(qū)中下侏羅統(tǒng)砂巖壓實(shí)和膠結(jié)作用減孔強(qiáng)度,在薄片微觀統(tǒng)計(jì)基礎(chǔ)上,對(duì)壓實(shí)損失孔隙度(Copl)、膠結(jié)損失孔隙度(Cepl)、壓實(shí)減孔強(qiáng)度(ICopl)和膠結(jié)減孔強(qiáng)度(ICepl)進(jìn)行了統(tǒng)計(jì)計(jì)算。計(jì)算公式如下(據(jù) Houseknecht,1987;Ehrenberg, 1989;Lundegard,1992)[1～3]:

式中:OP為砂巖原始孔隙度(%),一般取值為40%[1,4,5];IGV(%)為粒間體積(負(fù)膠結(jié)物孔隙度),其值為樣品總體積與骨架顆粒體積百分比之差,或等于雜基、膠結(jié)物與殘余原生粒間孔隙體積之和[5,6]; CEM(%)為粒間膠結(jié)物總量。

統(tǒng)計(jì)計(jì)算結(jié)果表明,砂巖膠結(jié)作用損失孔隙度均小于8%,平均為4%;壓實(shí)作用損失孔隙度均大于28%,壓實(shí)減孔強(qiáng)度高達(dá)80%以上(圖4)。由此可見,強(qiáng)烈的壓實(shí)作用是研究區(qū)中下侏羅統(tǒng)砂巖異常致密的主要原因。

圖4 中下侏羅統(tǒng)砂巖壓實(shí)與膠結(jié)減孔強(qiáng)度分析圖Fig.4 Statistical diagram showing the relative importance of compaction and cementation to reduction of porosity in Middle and Lower Jurassic sandstones

3 強(qiáng)壓實(shí)作用機(jī)理探討

川中地區(qū)中下侏羅統(tǒng)砂巖現(xiàn)今埋藏深度普遍較淺,一般在1 500～3 000 m之間,僅在北部坳陷低平構(gòu)造帶達(dá)到3 000～3 500 m,但強(qiáng)烈的壓實(shí)作用卻成為全區(qū)儲(chǔ)層異常致密的主要因素。筆者利用砂巖動(dòng)力成巖作用理論[7]研究方法,通過(guò)對(duì)砂巖原始成巖物質(zhì)組構(gòu)及其所處的盆地成巖動(dòng)力學(xué)因素系統(tǒng)分析,進(jìn)一步討論了研究區(qū)中下侏羅統(tǒng)砂巖強(qiáng)壓實(shí)作用機(jī)理,現(xiàn)分述如下。

3.1 內(nèi)因:砂巖原始成巖物質(zhì)組構(gòu)

據(jù)研究區(qū)大量鉆井巖心及薄片觀察,中下侏羅統(tǒng)砂巖碎屑粒度普遍偏細(xì),主要為細(xì)粒-極細(xì)粒級(jí)和粉砂級(jí)。砂巖碎屑成分上,除珍珠沖組及涼高山組發(fā)育少量高硅質(zhì)顆粒的巖屑石英砂巖之外,其它地區(qū)及層段均以高巖屑含量的巖屑砂巖類為主(圖5a),盡管各層段巖屑組成存在明顯差異(圖5b),但巖屑成分均為抗壓實(shí)能力差的塑性巖類(軟變質(zhì)巖類、云母、再旋回泥質(zhì)-粉砂級(jí)沉積巖和塑性火山巖等)。國(guó)內(nèi)外學(xué)者通過(guò)對(duì)不同粒度及成分砂巖與物性的關(guān)系研究統(tǒng)計(jì)和壓實(shí)實(shí)驗(yàn)表明,同粒度條件下,砂巖塑性巖屑含量越高越易壓實(shí)[8];而對(duì)于石英砂巖而言,粒度是控制壓實(shí)強(qiáng)度的主要因素,即顆粒粒度越細(xì)越易壓實(shí)、壓溶[9～11]。因此,偏細(xì)粒度使得研究區(qū)中下侏羅統(tǒng)砂巖在相同地質(zhì)背景下的巖屑砂巖和石英砂巖均表現(xiàn)出了強(qiáng)烈的壓實(shí)作用;同時(shí),高塑性巖屑含量導(dǎo)致巖屑砂巖壓實(shí)作用更為劇烈。

圖5 中下侏羅統(tǒng)砂巖碎屑成分三角圖Fig.5 Detrital compositional triangles of Middle and Lower Jurassic sandstones

3.2 外因:盆地成巖動(dòng)力學(xué)因素

1 )古深埋型埋藏成巖演化軌跡

通過(guò)對(duì)研究區(qū)不同構(gòu)造帶典型鉆井侏羅系沉積埋藏史恢復(fù),處于川中平緩構(gòu)造帶地區(qū)砂巖最大古埋深一般在3 500～4 000 m,而北部坳陷低平構(gòu)造帶地區(qū)最深可達(dá)5 000 m以上,均高出現(xiàn)今埋深達(dá)1 500 ～2 000 m。整體上,中下侏羅統(tǒng)含油砂巖經(jīng)歷了早期快速深埋期、持續(xù)深埋期和后期構(gòu)造抬升期三個(gè)埋藏成巖演化階段,具早期埋藏速率高,古埋藏深度大、持續(xù)深埋時(shí)間長(zhǎng)等特點(diǎn)(圖6)。壽建峰等[7]將該類砂巖埋藏成巖演化軌跡類型定義為古深埋型。古深埋型成巖演化軌跡導(dǎo)致研究區(qū)中下侏羅統(tǒng)砂巖強(qiáng)烈壓實(shí)作用的機(jī)理在于早期快速深埋使砂巖長(zhǎng)期處于深埋壓實(shí)中,原生孔隙急劇壓實(shí)降低及孔隙水快速排出;在進(jìn)入持續(xù)深埋期,由于早期孔隙水已大量排出大大降低了該期膠結(jié)作用強(qiáng)度,致使粒間缺乏膠結(jié)物膠結(jié)支撐作用,進(jìn)而促進(jìn)了機(jī)械壓實(shí)及壓溶作用的進(jìn)一步加劇。古深埋型熱演化軌跡導(dǎo)致強(qiáng)壓實(shí)作用在我國(guó)西部其它疊合盆地均得到證實(shí)。例如塔里木盆地英買2井和滿參1井,其志留系砂巖儲(chǔ)層現(xiàn)今埋藏深度相近,但英買2井砂巖熱演化軌跡為長(zhǎng)期淺埋、晚期快速深埋型,而滿參1井為古深埋型,因壓實(shí)作用強(qiáng)度不同導(dǎo)致的孔隙度差異可達(dá)7.0%;再如吐哈盆地哈密坳陷中上三疊統(tǒng)砂巖屬古深埋型,最大古埋深達(dá)4 500～5 000 m,而現(xiàn)今埋深在3 000m左右,砂巖因古埋藏深度大、埋藏速率高導(dǎo)致強(qiáng)烈壓實(shí)作用,壓實(shí)減孔量高達(dá)27.4%(原始孔隙度按40%計(jì)算)。

圖6 川中北部地區(qū)中下侏羅統(tǒng)砂巖埋藏成巖演化軌跡特征Fig.6 Burial diagenetic evolution paths of Middle and Lower Jurassic sandstones in the north of the study area

2 )較高古地溫場(chǎng)成巖環(huán)境

盆地地溫場(chǎng)對(duì)砂巖壓實(shí)作用的影響極其顯著,其中溫度對(duì)砂巖壓實(shí)作用的影響主要體現(xiàn)在,隨著溫度的升高,砂巖的可塑性增大及碎屑顆粒的抗壓強(qiáng)度降低[11～15]。壽建峰等[16]通過(guò)對(duì)盆地地溫場(chǎng)與砂巖壓實(shí)作用的關(guān)系研究發(fā)現(xiàn),在相同地層溫度下,因地溫梯度差異產(chǎn)生的熱效應(yīng)壓實(shí)作用大大提高了砂巖的壓實(shí)速率。對(duì)研究區(qū)中下侏羅統(tǒng)砂巖而言,地溫場(chǎng)對(duì)砂巖壓實(shí)作用的影響正是體現(xiàn)在較高的古地溫梯度上。四川盆地為今“冷盆”,鉆井測(cè)溫?cái)?shù)據(jù)獲得的現(xiàn)今地溫梯度一般為2.0～2.5℃/100m,然而其古地溫梯度卻整體較高,為古“熱盆”。據(jù)伍大茂、吳乃苓等[17]利用鏡質(zhì)體反射率法對(duì)四川盆地各地區(qū)古地溫計(jì)算結(jié)果,四川盆地古地溫梯度一般在2.5～5.5℃/ 100m之間(按現(xiàn)今地層厚度計(jì)算)。其中,研究區(qū)內(nèi)大部分地區(qū)最大古地溫梯度為2.5～3.3℃/100m;而東部靠近華鎣山西麓以川87井、羅11井和廣100井區(qū)為代表的地區(qū)最大古地溫梯度高達(dá) 5.47～ 12.35℃/100m?？梢?研究區(qū)中下侏羅統(tǒng)砂巖處于較高的古地溫場(chǎng)成巖環(huán)境之中。利用粒間體積保存深度與地溫梯度擬合關(guān)系求取了研究區(qū)古、今地溫梯度條件下的中下侏羅統(tǒng)砂巖粒間體積保存深度,公式如下[7,16]:

式中b=0.5093,Tgra為地溫梯度,排除溶孔和膠結(jié)物影響后壓實(shí)作用剩余的粒間體積IGV(或負(fù)膠結(jié)物孔隙度)一般在5%～10%之間。計(jì)算結(jié)果表明,在古地溫場(chǎng)環(huán)境中,以2.5～3.3℃/100m計(jì)算,中下侏羅統(tǒng)砂巖5%～10%粒間體積IGV對(duì)應(yīng)的保存深度大致在3 000～5 000 m之間,平均約為4 000 m(圖7,A區(qū)),與整個(gè)研究區(qū)的最大古埋藏深度吻合;若在現(xiàn)今地溫梯度2～2.5℃/100m條件下,其對(duì)應(yīng)的保存深度可延深至4 500～6 500 m,平均達(dá)5 500 m(圖7,B區(qū))。因此,研究區(qū)較高的古地溫場(chǎng)環(huán)境大大提高了中下侏羅統(tǒng)砂巖的壓實(shí)強(qiáng)度和壓實(shí)速率。

圖7 中下侏羅統(tǒng)砂巖粒間體積保存深度與地溫梯度關(guān)系Fig.7 Diagram showing strong correlation between IGV preservable depth and geothermal gradient of Middle and Lower Jurassic sandstone

3 )油氣充注滯后

大量文獻(xiàn)表明,油氣早期充注有利于深埋砂巖原生孔隙保存的主要機(jī)制有二,一為通過(guò)抑制或減緩粒間膠結(jié)作用來(lái)保存原生孔隙,該觀點(diǎn)最早由Johnson在1920年提出[18],目前被大多數(shù)學(xué)者所接受,我國(guó)學(xué)者近年來(lái)也有相關(guān)報(bào)道[19～21]。但在油氣充注能否有效抑制如石英、伊利石等自生礦物繼續(xù)沉淀、膠結(jié)上仍存在爭(zhēng)論[22～30];二為通過(guò)早期油氣充注形成的有效油氣圈閉而產(chǎn)生的異常高壓來(lái)抑制或減弱上覆地層壓實(shí)及壓溶作用來(lái)保存粒間體積[22,31,32]。川中地區(qū)中下侏羅統(tǒng)砂巖儲(chǔ)層段之上均發(fā)育厚層泥巖蓋層且早期構(gòu)造穩(wěn)定,如果在早期存在大規(guī)模油氣充注,那么砂巖儲(chǔ)層內(nèi)形成異常高壓進(jìn)而抑制或減弱壓實(shí)、壓溶作用將成為可能?，F(xiàn)今川中地區(qū)中下侏羅統(tǒng)砂巖油藏內(nèi)確實(shí)存在異常高壓,壓力系數(shù)為1.5～ 1.7[33]。然而在事實(shí)上,通過(guò)對(duì)下沙溪廟組、涼高山組砂巖儲(chǔ)層段成巖演化史及其下伏大安寨組主力烴源巖油氣演化史對(duì)比研究發(fā)現(xiàn),大安寨組烴源巖在晚白堊世成熟達(dá)到排烴高峰,而油氣開始大量充注于上部砂巖儲(chǔ)層更是晚在喜山運(yùn)動(dòng)構(gòu)造抬升期(圖8,包裹體均一溫度、成分和ESR測(cè)年數(shù)據(jù)引自鄭榮才, 1997)[34]。由此可見,研究區(qū)中下侏羅統(tǒng)現(xiàn)今地層異常高壓確與油氣大量充注關(guān)系密切,但形成滯后于砂巖儲(chǔ)層壓實(shí)致密化時(shí)間,未能在早期快速深埋和持續(xù)深埋壓實(shí)期對(duì)儲(chǔ)層壓實(shí)、壓溶作用起到有效抑制或減弱作用。因此,油氣充注滯后在一定意義上也是導(dǎo)致研究區(qū)下沙溪廟組和涼高山組砂巖儲(chǔ)層壓實(shí)強(qiáng)烈的重要因素。

圖8 中下侏羅統(tǒng)砂巖儲(chǔ)層成巖演化史與烴源巖熱演化史關(guān)系圖Fig.8 Diagram showing the relationship between sandstone diagenetic evolution and thermal evolution of source rocks in Middle and Lower Jurassic

4 結(jié)論

(1)研究區(qū)中下侏羅統(tǒng)砂巖儲(chǔ)層普遍異常致密,孔隙度平均小于5%,滲透率遠(yuǎn)小于1 X 10-3μm2,為典型的超低孔、超低滲儲(chǔ)層,壓實(shí)(壓溶)作用為砂巖致密主要原因。

(2)研究區(qū)中下侏羅統(tǒng)砂巖強(qiáng)壓實(shí)成巖作用機(jī)理主要包括兩個(gè)方面:一為偏細(xì)粒度、高易壓實(shí)塑性巖屑為主導(dǎo)的砂巖原始成巖物質(zhì)組構(gòu)成為了砂巖易于壓實(shí)的內(nèi)在因素;二為古深埋型埋藏成巖演化軌跡、較高古地溫場(chǎng)成巖環(huán)境、油氣充注滯后的盆地成巖動(dòng)力學(xué)特征是砂巖壓實(shí)作用強(qiáng)烈的主要外因。

(3)砂巖動(dòng)力成巖作用理論研究方法將碎屑巖的成巖作用置于整個(gè)盆地的動(dòng)力學(xué)環(huán)境中,在整體上系統(tǒng)考慮碎屑巖成巖、孔隙演化與其內(nèi)在的成巖物質(zhì)特征和外在的盆地構(gòu)造、熱流、流體等成巖動(dòng)力學(xué)特征之間的時(shí)、空動(dòng)態(tài)聯(lián)系性,在解決我國(guó)西部疊合盆地復(fù)雜儲(chǔ)層成因機(jī)理上起到了良好的指導(dǎo)作用。

References)

1 Houseknecht D W.Assessing the relative importance of compaction processes and cementation to reduction of porosity in sandstones[J].APG Bulletin,1987,71:633-642

2 Ehrenberg SN.Assessing the relative importance of compaction processes and cementation to reduction of porosity in sandstones:discussion; compaction and porosity evolution of Pliocene sandstones,Ventura basin,California:discussion[J].APG Bulletin,1989,73:1274-1276

3 Lundegard PD.Sandstone porosity loss-a“big picture”view of the importance of compaction[J].ournal of Sedimentary Petrology,1992, 62:250-260

4 Beard D C,Weyl PK.Influence of texture on porosity and permeability of unconsolidated sand[J].APG Bulletin,1973,57:349-369

5 Wilson JC,McBride E F.Compaction and porosity evolution of Pliocene sandstones,Ventura basin,California[J].APG Bulletin, 1988,72:664-681

6 Paxton ST,Szabo JO,Ajdukiewicz JM,Klimentidis R E.Construction of an intergranular volume compaction curve for evaluating and predicting compaction and porosity loss in rigid-grain sandstone reservoirs [J].APG Bulletin,2002,86:2047-2067

7 壽建峰,張惠良,斯春松,等。砂巖動(dòng)力成巖作用[M]。北京:石油工業(yè)出版社,2005:48-62[Shou Jianfeng,Zhang Huiliang,Si Chunsong,et al.Dynamic Diagenesis of Sandstone[M].eijing:Petroleum Industry Press,2005:48-62]

8 Pittman ED,Larese R E.Compaction of lithic sands:experimental results and applications[J].APG Bulletin,1991,75(8):1279-1299

9 Porter EW,James W C.Influence of pressure,salinity,temperature and grain size on silica diagenesis in quartzose sandstones[J].hemical Geology,1986,57:59-369

10 Houseknecht D W.Intergranular pressure solution in four quartzose sandstones[J].ournal of Sedimentary Petrology,1988,58:228-246

11 Dewers T,Hajash A.Rate laws for water-assisted compaction and stress-induced water-rock interaction in sandstones[J].ournalof Geophysical Research,1995,100:13093-13112

12 Handin J,Hager R V.Experimental deformation of sedimentary rocks under confining pressure:tests at high temperature[J].APG Bulletin,1958,42:2892-2934

13 Maxwell JC.Influence of depth,temperature,and geologic age on porosity of quartzose sandstone[J].APG Bulletin,1964,48(5): 697-709

14 Schmoker JW,Gautier D L.Sandstone porosity as function of thermal maturity-an approach to porosity comparison and prediction[J].eology,1988,16(11):1697-1703

15 Schmoker JW,Gautier D L.Compaction of basin sediments:Modeling based on time-temperature history[J].ournal of Geophysical Research,1989,94(B):7379-7386

16 壽建峰,朱國(guó)華。砂巖儲(chǔ)層孔隙保存的定量預(yù)測(cè)研究[J]。地質(zhì)科學(xué),1998,32(2):244-249[Shou Jianfeng,Zhu Guohua.Study on quantitative prediction of porosity preservation in sandstone reservoirs[J].cientia Geologica Sinica,1998,32(2):244-249]

17 伍大茂,吳乃苓,郜建軍。四川盆地古地溫研究及其地質(zhì)意義[J]。石油學(xué)報(bào),1998,19(1):18-23[Wu Damao,Wu Nailing, Gao Jianjun.Paleogeotemperature in Sichuan Basin and its geological significance[J].cta Petrolei Sinica,1998,19(1):18-23]

19 王琪,史基安,肖立新,等。石油侵位對(duì)碎屑儲(chǔ)集巖成巖序列的影響及其與孔隙演化的關(guān)系一以塔西南石炭系石英砂巖為例[J]。沉積學(xué)報(bào),1998,16(3):97-101[Wang Qi,Shi Ji'an,Xiao Lixin,et al.Influence of oil emplacement on diagenetic sequence of the clastic reservoir rock and its relationship to the porosity evolutiontaking the Carboniferous quartz sandstone in southwest Tarim depression asan example[J].cta Sedimentologica Sinica,1998,16(3): 97-101]

20 蔡春芳,顧家裕,蔡洪美。塔中地區(qū)志留系烴類侵位對(duì)成巖作用的影響[J]。沉積學(xué)報(bào),2001,19(1):60-65[Cai Chunfang,Gu Jiayu,Cai Hongmei.Effect of hydrocarbon emplacement on diagenesis of Silurian sandstone of central Tarim Basin[J].cta Sedimentologica Sinica,2001,19(1):60-65]

21 羅靜蘭,劉小洪,林潼,等。成巖作用與油氣侵位對(duì)鄂爾多斯盆地延長(zhǎng)組砂巖儲(chǔ)層物性的影響[J]。地質(zhì)學(xué)報(bào),2006,80(5): 664-673[Luo Jinglan,Liu Xiaohong,Lin Tong,etal.Impact of diagenesis and hydrocarbon emplacementon sandstone reservoir quality of the Yanchang formation(Upper Triassic)in the Ordos basin[J].cta Geologica Sinica,2006,80(5):664-673]

22 Hawkins P J.Relationship between diagenesis,porosity reduction, and oil emplacement in late Carboniferous sandstone reservoirs,Bothamsall oilfield,E.Midlands[J].ournal of the Geological Society, 1978,135:7-24

23 Saigal G C,Bjφrlykke K,Larter S.The effects of oil emplacement indiagenetic processes-example from the Fulmar reservoir sandstones, central North Sea[J].APG Bulletin,1992,76:1024-1033

24 Nedkvitne T,Karlsen D A,Bjφrlykke K,etal.Relationship between reservoir diagenetic evolution and petroleum emplacement in the Ulafield,North Sea[J].arine and Petroleum Geology,1993,10: 255-270

25 Worden R H,Oxtoby N H.Does oil emplacement stop diagenesis in sandstone reservoirs?[M].uropean Association of Geoscientists and Engineers Conference and Technical Exhibition,European Association of Petroleum Geoscientists and Engineers Division paper F044,1995, unpaginated

26 Worden R H,Oxtoby N H,Smalley P C.Can oil emplacement prevent quartz cementation in sandstones[J].etroleum Geoscience, 1998,4:129-137

27 Midtb R E A,Rykkje JM,Ramm M.Deep burial diagenesisand reservoir quality along the eastern flank of the Viking Graben:evidence for illitization and quartz cementation after hydrocarbon emplacement [J].lay Minerals,2000,35:231-241

28 Bloch S,Lander R H,L.Bonnell.Anomalously high porosity and permeability in deeply buried sandstone reservoirs:Origin and predictability[J].APG Bulletin,2002,86:301-328

29 Marchand A M E,Smalley PC,Haszeldine R S,et al.Note on the importance of hydrocarbon fill for reservoir quality prediction in sandstones[J].APG Bulletin,2002,86:1561 1571。

30 Molenaar N,Cyziene J,Sliaupa S,et al.Lack of inhibiting effect of oil emplacement on quartz cementation:Evidence from Cambrian reservoir sandstones,Paleozoic Baltic Basin[J].eological Society of America Bulletin,2008,120:1280-1295

31 O Brien JJ,Lerche I.The preservation of porosity through hydrocarbon entrapment during burial:Society of Petroleum Engineers Formation Evaluation,1986,1(3):295-299

32 Osborne M J,Swarbrick R E.Mechanisms for generating overpressure in sedimentary basins:a reevaluation[J].APG Bulletin,1997, 81:1023-1041

33 謝繼容,張健,魏小薇,等。公山廟沙一段油氣藏低孔滲儲(chǔ)層產(chǎn)油機(jī)理研究[J]。天然氣工業(yè),2003,23(3):34-37[Xie Jirong, Zhang Jian,Wei Xiaowei,et al.Oil producing mechanism study of Sha-1 low porosity and low permeability reservoirs in Gongshanmiao oilfield,Sichuan basin[J].aturalGas Industry,2003,23(3):34-37]

34 鄭榮才,劉文均,李安仁。川北下侏羅統(tǒng)自流井組大安寨段灰?guī)r非常規(guī)儲(chǔ)層包裹體研究[J]。地質(zhì)論評(píng),1997,43(5):515-523 [Zheng Rongcai,Liu Wenjun,LiAnren.Fluid inclusion study of unconventional reservoirs in limestone of the Da'anzhaimember of the lower jurassic Ziliujing Formation in northern Sichuan[J].eological Review,1997,43(5):515-523]

Origin M echanism of Anomalous Tightness of M iddle and Lower Jurassic Sandstone Reservoirs in Central Sichuan Basin

LIU Zhan-guo SIChun-song SHOU Jian-feng NIChao PAN Li-yin LIU Qun
(Hangzhou Research Institute of Geology,PetroChina,Hangzhou 310023)

As unique tight reservoirs in China,themiddle-upper Jurassic sandstones in central Sichuan basin occur at present-day burial depth of 1 500～3 000 m and they are characterized by ultra-low porosity(average below 5%) and ultra-low permeability(average below 1 X10-3μm2)that fail tomatch their burial depth.Microscopic observation and statistics of relative contribution of compaction and cementation to porosity loss indicate that intensive compaction is responsible for the anomalous tightness of these sandstones.Furthermore,utilizing the research method of sandstone dynamical diagenesis theory,based on the analysis of original sandstone components and basin diagenetic dynamic factors,themechanism of intensive compaction ofMiddle and Lower Jurassic sandstones in the study area has been discussed.It is suggested that fine grain size and high ductile fragments content are the internal cause,while the basin diagenetic dynamics characteristics of deep paleo-burial,high paleo-geothermal field and late oil emplacement are considered as the external cause.

Mechanisms of diagenesis and porosity evolution of some sandstone reservoirs are quite complex in superimposed basins in western China.In one of these complex cases,this study of originmechanism of anomalous tightness of Middle and Lower Jurassic sandstone reservoirs in central Sichuan Basin shows that the sandstone dynamical diagenesis theory and method can integrally and systematically take original sandstone components and all basin diagenetic dynamics factors(structure,thermal flow,pore fluid,etc。)into account,and which can well resolve such difficult questions in complex sandstone reservoirs。

Sichuan basin;tight sandstone reservoir;compaction;dynamic diagenesis theory

劉占國(guó) 男 1980年出生 工程師 碩士 儲(chǔ)層地質(zhì)學(xué) E-mail:liuzg_hz@petrochina.com.cn

TE122.2+21

A

1000-0550(2011)04-0744-08

2010-06-13;收修改稿日期:2010-09-20