大北-克深區(qū)塊致密砂巖氣藏水鎖傷害防治

江 昀，楊賢友，李 越，石 陽，許國(guó)慶，余 玥

1)中國(guó)石油勘探開發(fā)研究院， 北京 100083；2)中海石油(中國(guó))有限公司天津分公司，天津 300459；3)中國(guó)石油西南油氣田分公司川中油氣礦，四川遂寧 629000

【環(huán)境與能源/EnvironmentandEnergy】

大北-克深區(qū)塊致密砂巖氣藏水鎖傷害防治

江 昀1，楊賢友1，李 越2，石 陽1，許國(guó)慶1，余 玥3

1)中國(guó)石油勘探開發(fā)研究院， 北京 100083；2)中海石油(中國(guó))有限公司天津分公司，天津 300459；3)中國(guó)石油西南油氣田分公司川中油氣礦，四川遂寧 629000

針對(duì)大北-克深區(qū)塊致密砂巖儲(chǔ)層易發(fā)生水鎖傷害從而降低氣井產(chǎn)能，研究目標(biāo)區(qū)塊水鎖傷害機(jī)理及相應(yīng)防治措施．基于氣相相對(duì)滲透率建立水鎖指數(shù)(water block index, WBI)，分析水鎖傷害程度及其影響因素，優(yōu)選耐高溫表面活性劑體系防治水鎖傷害．結(jié)果表明，目標(biāo)區(qū)塊巖心水鎖傷害程度屬?gòu)?qiáng)水鎖型(平均WBI為69.8%)，基質(zhì)滲透率、驅(qū)替壓力均與 WBI呈負(fù)相關(guān)，含水飽和度、黏土礦物含量、流體黏度和表面張力均與WBI呈正相關(guān)，優(yōu)選出耐溫復(fù)配表面活性劑體系JY-2(由質(zhì)量分?jǐn)?shù)為0.05%的FC-25和質(zhì)量分?jǐn)?shù)為15%的甲醇組成)和JY-3(由質(zhì)量分?jǐn)?shù)為0.5%的HSC-25和質(zhì)量分?jǐn)?shù)為15%的甲醇組成)，JY-3效果更好，可將目標(biāo)區(qū)塊巖心水鎖指數(shù) WBI從66.2%降至28.4%，達(dá)到解除水鎖傷害目的．

水鎖傷害；氣相相對(duì)滲透率；水鎖指數(shù)；水鎖影響因素；耐高溫復(fù)配表面活性劑；解除水鎖

致密砂巖氣藏?fù)碛芯薮箝_發(fā)潛力，是未來中國(guó)非常規(guī)油氣發(fā)展的重點(diǎn)，但其單井自然產(chǎn)能低，需要通過一定技術(shù)措施達(dá)到實(shí)現(xiàn)經(jīng)濟(jì)開采[1]．增產(chǎn)改造過程中會(huì)出現(xiàn)一系列儲(chǔ)層傷害問題(如微粒運(yùn)移傷害、流體不配伍和水鎖傷害等)，尤其當(dāng)儲(chǔ)層為高溫高壓環(huán)境時(shí)，問題變得更復(fù)雜，嚴(yán)重限制了致密砂巖氣藏的有效開發(fā)．

大北-克深區(qū)塊位于塔里木盆地北部，目的層巴什基奇克組以細(xì)粒長(zhǎng)石巖屑砂巖為主，巖屑砂巖、巖屑長(zhǎng)石砂巖次之．儲(chǔ)集空間包括殘余原生粒間孔、溶孔、溶蝕縫和微孔隙等．儲(chǔ)層內(nèi)發(fā)育高角度裂縫，裂縫內(nèi)方解石和白云石為主要充填礦物．黏土礦物總量約14.1%～19.2%，相對(duì)含量最高的為伊利石(67%～74%)，其次為伊蒙混層(16%～22%)，最少為綠泥石(5%～13%)．伊利石和蒙脫石大量存在會(huì)導(dǎo)致束縛水飽和度增加，孔隙半徑變小，氣體滲流阻力增大，儲(chǔ)層存在潛在水鎖傷[2-4]．基質(zhì)滲透率為0.01×10-3～0.50×10-3μm2，孔隙度為2.09%～7.91%，壓力系數(shù)為1.54～1.65，地溫梯度為0.021 ℃/m(儲(chǔ)層埋深為5 500～7 500 m，溫度為150～170 ℃)，平均孔喉半徑為0.1 μm，屬于高溫高壓低孔低滲致密砂巖儲(chǔ)層．

針對(duì)水鎖傷害問題，文獻(xiàn)[5-8]開展了大量室內(nèi)實(shí)驗(yàn)和現(xiàn)場(chǎng)應(yīng)用研究．基于核磁共振技術(shù)研究的滲吸機(jī)理表明，水鎖傷害主要原因?yàn)楦呙芰9]，其影響因素包括滲透率、潤(rùn)濕性和溫度等[10]．基于上述研究成果，大量防水鎖體系相繼提出，包括降低表面張力[11]，改變潤(rùn)濕性[12-16]和降低含水飽度[17-20]等．

本文以塔里木盆地大北-克深區(qū)塊6口井巖心樣品為研究對(duì)象，基于氣相穩(wěn)態(tài)法滲流模型建立水鎖指數(shù)(water block index, WBI)，分析水鎖傷害程度及其影響因素，優(yōu)選耐溫復(fù)配表面活性劑體系進(jìn)行水鎖傷害防治．

1 實(shí)驗(yàn)樣品及儀器

實(shí)驗(yàn)樣品：25塊巖心(直徑為2.54 cm，長(zhǎng)為4.06～5.08 cm) 取自大北-克深區(qū)塊6口井(5 850.3～5 885.8 m)；4種表面活性劑均購(gòu)自美國(guó)3M公司．

實(shí)驗(yàn)儀器：DCAT11表面張力測(cè)試儀；DSA-30潤(rùn)濕角測(cè)定儀；自制自吸實(shí)驗(yàn)裝置；高溫高壓酸化反應(yīng)模擬裝置；轉(zhuǎn)向均勻酸化多功能驅(qū)替模擬裝置．

2 實(shí)驗(yàn)方法

2.1 水鎖傷害評(píng)價(jià)實(shí)驗(yàn)

選取11塊巖心測(cè)定氣相相對(duì)滲透率，建立WBI評(píng)價(jià)水鎖傷害程度．實(shí)驗(yàn)步驟如下：① 巖心置于烘箱中，溫度為50 ℃，持續(xù)24 h；② 取出巖心，稱其干質(zhì)量m0， 按式(1)計(jì)算初始?xì)庀酀B透率K0； ③ 巖心置于夾持器中，使用模擬地層水持續(xù)驅(qū)替12 h，稱其濕質(zhì)量m1； ④ 連續(xù)注入N2驅(qū)替50～60 h，直到巖心質(zhì)量變化小于3%，每隔0.5～1 h記錄巖心質(zhì)量(mi，i=2,3,…,n)， 按式(2)計(jì)算不同時(shí)間含水飽和度Sw； ⑤ 參照行業(yè)標(biāo)準(zhǔn)SY/T 5345—2007，根據(jù)非穩(wěn)態(tài)法計(jì)算不同含水飽和度下氣相滲透率Ki；⑥ 按式(3)計(jì)算水鎖指數(shù)WBI，評(píng)價(jià)水鎖傷害程度，并繪制含水飽和度Sw與氣相相對(duì)滲透率Krg關(guān)系曲線．

(1)

(2)

(3)

其中，mi為不同時(shí)間記錄的巖心質(zhì)量(單位：g)；Qg為氣體流速(單位：cm3/s)；μg為氣體黏度(單位：mPa/s)；L為巖心長(zhǎng)度(單位：cm)；A為巖心橫截面積(單位：cm2)；pinlet和poutlet分別為入口及出口壓力(單位：MPa)；WBI為水鎖指數(shù)(單位：%)；K0為巖心初始?xì)庀酀B透率(單位：μm2)；Kn為束縛水飽和度下氣相滲透率(單位：μm2)．

WBI介于0～30%，水鎖傷害程度弱；WBI介于30%～60%，水鎖傷害程度較弱；WBI介于60%～90%，水鎖傷害程度強(qiáng)；WBI為90%以上，水鎖傷害程度極強(qiáng)．

2.2 耐溫復(fù)配表面活性劑體系優(yōu)選

選用DCAT11表面張力測(cè)試儀，根據(jù)鉑金板法，在25 ℃下測(cè)試4種表面復(fù)配體系表面張力；選用DSA-30潤(rùn)濕角測(cè)定儀，根據(jù)接觸角法在25 ℃下測(cè)定巖石潤(rùn)濕角，觀察巖心原始狀態(tài)和添加表面活性劑后潤(rùn)濕性能；選用自制巖心自吸實(shí)驗(yàn)裝置(圖1)通過巖心含水飽和度變化規(guī)律，判斷解水鎖劑是否能夠縮短排液時(shí)間．

圖1 自發(fā)滲吸實(shí)驗(yàn)裝置Fig.1 (Color online) Experimental apparatus of spontaneous imbibition

2.3 水鎖傷害解除實(shí)驗(yàn)

利用優(yōu)選的復(fù)配表面活性劑進(jìn)行水鎖傷害解除評(píng)價(jià)實(shí)驗(yàn)，步驟如下：① 25 ℃下巖心用模擬地層水進(jìn)行抽真空飽和；② 巖心裝入巖心夾持器內(nèi)，電加熱套升溫至160 ℃，沿氣測(cè)的反方向注入2倍孔隙體積的復(fù)配表面活性劑，密閉冷卻巖心至25 ℃；③ 取出巖心，用試紙將巖心表面流體吸干，稱量巖心濕質(zhì)量；④ 巖心放入巖心夾持器內(nèi)，25 ℃下正向持續(xù)注入N2驅(qū)替，至巖心質(zhì)量不再變化，測(cè)量不同含水飽和度下氣相相對(duì)滲透率．

3 結(jié)果與討論

3.1 水鎖指數(shù)

選取11塊巖心進(jìn)行水鎖傷害評(píng)價(jià)實(shí)驗(yàn)，巖心物性參數(shù)及水鎖指數(shù)如表1，Swir為初始含水飽和度．由表1可見，巖心孔隙度為2.09%～7.91%，平均孔隙度為5.04%，滲透率為0.011×10-3～0.424×10-3μm2，平均滲透率為0.098×10-3μm2，屬低孔低滲巖心．水鎖指數(shù)為45.52%～87.50%，平均水鎖指數(shù)為69.8%，屬于強(qiáng)水鎖型．

表1 巖心物性參數(shù)及水鎖指數(shù)

3.2 影響因素

3.2.1 含水飽和度

Krg在不同Sw下計(jì)算結(jié)果如圖2．由圖2可見，當(dāng)Sw介于40%～80%時(shí)，Krg隨Sw增加顯著降低，曲線呈下凸?fàn)睿划?dāng)Sw介于80%～100%時(shí)，Krg變化幅度不大，均小于15%．水鎖傷害程度隨Sw的增加呈現(xiàn)先增加后趨于穩(wěn)定的規(guī)律．

圖2 巖心氣相相對(duì)滲透率測(cè)試結(jié)果Fig.2 (Color online) Krg of 11 cores under different Sw

3.2.2 基質(zhì)滲透率

分別測(cè)定3#、11#和18#巖心(滲透率分別為0.424×10-3、0.016×10-3和0.031×10-3μm2)的Krg和WBI，結(jié)果如圖3．由圖3可見，巖心基質(zhì)滲透率越高，Krg越高，WBI越低．這是由于基質(zhì)滲透率越高，相應(yīng)孔喉半徑越大，毛管力越小，侵入流體更容易被驅(qū)替，滯留流體更少，水鎖傷害程度越低．

圖3 3#、8#和11#巖心氣相相對(duì)滲透率及水鎖指數(shù)Fig.3 (Color online) Krg and WBI of 3#, 8# and 11#

3.2.3 黏土礦物含量

分別測(cè)定基質(zhì)滲透率相近、黏土礦物質(zhì)量分?jǐn)?shù)為14.9%、20.1%和23.6%的6#、7#和11#巖心的Krg以及WBI，結(jié)果如圖4．由圖4可見，黏土礦物質(zhì)量分?jǐn)?shù)越高(尤其是伊利石及伊蒙混層質(zhì)量分?jǐn)?shù)高)，水鎖傷害程度越大．這是由于絲狀伊利石和蒙脫石的強(qiáng)吸水作用導(dǎo)致束縛水飽和度高，增大了流體運(yùn)移難度，造成流體滯留．

圖4 6#、7#和11#巖心氣相相對(duì)滲透率及水鎖指數(shù)Fig.4 (Color online) Krg and WBI of 6#, 7# and 11#

3.2.4 驅(qū)替壓力

選用巖心物性相近的4#和5#巖心，對(duì)比不同驅(qū)替壓力(1 MPa和2 MPa)對(duì)水鎖傷害程度影響，結(jié)果如圖5．由圖5可見，當(dāng)驅(qū)替時(shí)間足夠長(zhǎng)，5#巖心Sw下降速率快于4#，即驅(qū)替壓力影響排液時(shí)間，驅(qū)替壓力越大，Sw越低，水鎖傷害程度越低．

圖5 4#和5#巖心含水飽和度曲線Fig.5 (Color online) Water saturation curves of 4# and 5#

3.2.5 注入流體類型

選取15#、16#和25#巖心，對(duì)比注入不同流體水鎖傷害程度，結(jié)果見表2．由表2可以看出，3種流體對(duì)滲透率傷害程度依次為：表面活性劑JY-2<模擬地層水(A)<胍膠壓裂液濾液(B)．影響流體性質(zhì)主要因素為黏度(μ)和表面張力(σ)， 黏度越高，表面張力越大，毛管力越大，侵入流體越難排出．

表2 不同驅(qū)替流體水鎖指數(shù)

根據(jù)水鎖傷害程度評(píng)價(jià)結(jié)果以及對(duì)水鎖指數(shù)影響因素分析可知，基質(zhì)滲透率和驅(qū)替壓力與水鎖指數(shù)呈負(fù)相關(guān)，含水飽和度、黏土礦物質(zhì)量分?jǐn)?shù)、流體黏度和表面張力與水鎖指數(shù)呈正相關(guān)．

3.3 復(fù)配表面活性劑體系優(yōu)選

根據(jù)拉普拉斯公式可知，在孔喉尺寸不發(fā)生變化前提下，毛細(xì)力與表面張力和潤(rùn)濕角均呈線性關(guān)系．解除水鎖傷害主要從改變潤(rùn)濕性和降低表面張力兩個(gè)角度出發(fā)．結(jié)合大北-克深區(qū)塊儲(chǔ)層地質(zhì)特征，選取的表面活性劑需要滿足如下要求：① 低表面張力(30 mN·m-1以下)；② 將巖石由水濕轉(zhuǎn)為中性潤(rùn)濕(75°～105°)，并使長(zhǎng)時(shí)間保持相對(duì)穩(wěn)定的潤(rùn)濕性；③ 良好耐溫性能(160 ℃以上)和耐鹽性能；④ 起泡性低．據(jù)此初步選擇氟碳表面活性劑(FC4430和FS-31)、陽離子表面活性劑(HSC-25)和生物表面活性劑(F108)共4種耐溫表面活性劑進(jìn)行測(cè)試．采用表面活性劑與甲醇類復(fù)配體系(表面活性劑降低表面張力并改變巖心潤(rùn)濕性，大幅度降低毛管力；甲醇在較短時(shí)間內(nèi)將儲(chǔ)層內(nèi)流體蒸發(fā)，降低含水飽和度)．4種體系配方分別為：① JY-1，由質(zhì)量分?jǐn)?shù)為0.05%的FC4430和質(zhì)量分?jǐn)?shù)為15%甲醇組成；② JY-2，由質(zhì)量分?jǐn)?shù)為0.05%的FS-31和質(zhì)量分?jǐn)?shù)為15%甲醇組成；③ JY-3，由質(zhì)量分?jǐn)?shù)為0.5%的HSC-25和質(zhì)量分?jǐn)?shù)為15%甲醇組成；④ JY-4，由質(zhì)量分?jǐn)?shù)為0.5%的F108和質(zhì)量分?jǐn)?shù)為15%甲醇組成．

3.3.1 表面張力測(cè)試

將高溫反應(yīng)后樣品與室溫下樣品表面張力進(jìn)行對(duì)比，如表3．由表3可見，4種復(fù)配表面活性劑均能滿足耐溫需求，在180 ℃下能夠長(zhǎng)期保持良好的活性，能滿足要求，且與室溫樣品相比，表面張力略有提升．

表3 復(fù)配表面活性劑表面張力

3.3.2 潤(rùn)濕性測(cè)試

復(fù)配表面活性劑在巖心表面吸附方式主要為定向吸附．極性基朝向固體，疏水基朝向氣體，從而吸附在固體表面并形成定向排列的吸附層，使自由能較高的固體界面轉(zhuǎn)化為低能界面，達(dá)到改變潤(rùn)濕性目的．測(cè)試結(jié)果如圖6．從圖6可以看出，JY-1和JY-4可將水濕巖石(潤(rùn)濕角20°～30°)潤(rùn)濕角增大至60°～65°，JY-2和JY-3可將潤(rùn)濕角增大至70°～78°，JY-2和JY-3改變潤(rùn)濕性的性能優(yōu)于JY-1和JY-4．

圖6 添加表面活性劑前后潤(rùn)濕性結(jié)果Fig.6 (Color online) Wettability before and after adding surfactants

3.3.3 自發(fā)滲吸實(shí)驗(yàn)

針對(duì)不同儲(chǔ)層巖心的孔隙度、孔喉尺寸及形狀不同問題，自吸實(shí)驗(yàn)選用對(duì)比含水飽和度與時(shí)間關(guān)系曲線，對(duì)比模擬地層水(A)、復(fù)配表面活性劑JY-2/JY-3與模擬地層水混合液(B)以及預(yù)處理體系JY-2/JY-3+混合液B(C)3種情況下巖心自發(fā)滲吸曲線，結(jié)果如圖7．由圖7可見，使用B和C均能使自吸速率和自吸平衡含水飽和度降低，自吸進(jìn)入儲(chǔ)層流體質(zhì)量減少，對(duì)自吸過程起抑制作用．

結(jié)合表面張力測(cè)試，潤(rùn)濕性測(cè)試和自發(fā)滲吸實(shí)驗(yàn)結(jié)果，優(yōu)選耐溫復(fù)配表面活性劑體系JY-2和JY-3，進(jìn)行水鎖傷害防治評(píng)價(jià)．

圖7 21#和22#巖心自發(fā)滲吸曲線Fig.7 (Color online) Spontaneous imbibition results of 21# and 22#

4 水鎖傷害

注入JY-2和JY-3后，測(cè)定相應(yīng)水鎖指數(shù)變化，結(jié)果如圖8．由圖8可見，注入JY-2后，WBI由62.6%降至42.4%，水鎖傷害程度屬于較弱型；注入JY-3后，WBI由66.2%降至28.4%，屬于弱水鎖型，即注入JY-3能達(dá)到防治水鎖傷害目的．

圖8 JY-2和JY-3的水鎖指數(shù)Fig.8 (Color online) WBIs of JY-2 and JY-3

5 結(jié) 論

綜上研究可知：

1)根據(jù)水鎖指數(shù)評(píng)價(jià)水鎖傷害程度，得到目標(biāo)區(qū)塊巖心水鎖傷害程度達(dá)70%，屬于強(qiáng)水鎖型．

2)含水飽和度越低、滲透率值越大、黏土礦物含量越少、表面張力越小、驅(qū)替壓力越大，水鎖傷害程度越低．

3)通過表面張力測(cè)試，潤(rùn)濕性測(cè)試和自發(fā)滲吸實(shí)驗(yàn)優(yōu)選耐溫復(fù)配表面活性劑體系JY-2(由質(zhì)量分?jǐn)?shù)為0.05的FS-31和質(zhì)量分?jǐn)?shù)為15%的甲醇組成)和JY-3(由質(zhì)量分?jǐn)?shù)為0.5%的HSC-25和質(zhì)量分?jǐn)?shù)為15%的甲醇組成)，注入JY-3后，水鎖指數(shù)由66.2%降至28.4%，可由強(qiáng)水鎖型轉(zhuǎn)變?yōu)槿跛i型，能達(dá)到防治水鎖傷害目的．

引文：江 昀，楊賢友，李 越，等． 大北-克深區(qū)塊致密砂巖氣藏水鎖傷害防治[J]. 深圳大學(xué)學(xué)報(bào)理工版，2017，34(6)：640-646.

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【中文責(zé)編：晨兮；英文責(zé)編：天瀾】

2017-03-18；Revised2017-08-22；Accepted2017-09-18

Professor Yang Xianyou．E-mail: yangxianyou@petrochina.com.cn

SolutionsforwaterblockdamageoftightgasreservoirsinDabei-Keshenarea

JiangYun1,YangXianyou1,LiYue2,ShiYang1,XuGuoqing1,andYuYue3

1) Research Institute of Petroleum Exploration & Development, PetroChina, Beijing 100083, P.R.China2) CNOOC(China)Co. Ltd. Tianjin Branch, Tianjin 300459, P.R.China3) Chuanzhong Division of PetroChina Southwest Oil & Gas Field Company, Suining 629000, Sichuan Province, P.R.China

Water block damage is likely to occur in tight gas reservoirs of Dabei-Keshen area and decreases production of gas wells. In order to investigate the mechanisms of water block and the corresponding measures, the water block index (WBI) is developed to appraise the damage degree of water block in approach of relative gas permeability, and composite surfactant system is optimized to clean up effects of water block damage through interfacial tension tests, wettability tests and spontaneous imbibition experiments. The results and conclusions are as follows: the average WBI for core samples from the targeted zone is 69.8%, belonging to the type of strong damage of water block. Sensitivity analysis shows matrix permeability and displacement pressure are in negative correlation with WBI, while water saturation, content of clays, fluid viscosity and interfacial tension are in positive correlation with WBI. In this work, thermo-stable surfactant systems JY-2(0.05% FS-31+15% methanol) and JY-3(0.5% HSC-25+15% methanol) are developed. JY-3 performs better in reducing WBI from 66.2% to less than 28.4%. Surfactants in the composite system contributes to reducing the interfacial tension and altering wettability, and methanol is beneficial to reducing water saturation through accelerating evaporation shortly. The synergy effect promotes the cleanup process of water block damage. The found mechanisms of water block damage and numerous experimental data provide us valuable insight on the economic and efficient development of gas fields.

water block damage; relative gas permeability; water block index; sensitivity analysis; thermo-stable composite surfactant system; cleanup of water block

Foundation：National Science and Technology Major Project of China (2011ZX05046005)

：Jiang Yun, Yang Xianyou, Li Yue, et al．Solutions for water block damage of tight gas reservoirs in Dabei-Keshen area[J]. Journal of Shenzhen University Science and Engineering, 2017, 34(6): 640-646.(in Chinese)

TE 355

A

10.3724/SP.J.1249.2017.06640

國(guó)家科技重大專項(xiàng)資助項(xiàng)目(2011ZX05046005)

江 昀(1990—)，男，中國(guó)石油勘探開發(fā)研究院博士研究生．研究方向：儲(chǔ)層改造．E-mail：jiangyun119@petrochina.com.cn