Application of multipole array sonic logging to acid hydralic fracturing

Multipole array sonic logging tools have widely been employed in Chinese oilfields in recent years. We have developed a software package for rock mechanical analysis with multipole array sonic logs. This advanced data processing method and software have been applied to the Tahe oilfield in Northern West China to provide guidance to acid hydraulic fracturing design and evaluation. In this paper, we present the field examples of such data processing and applications to demonstrate the validity and advantages of our method and software package.

Predicting gas-bearing distribution using DNN based on multi-component seismic data: Quality evaluation using structural and fracture factors

The tight-fractured gas reservoir of the Upper Triassic Xujiahe Formation in the Western Sichuan Depression has low porosity and permeability. This study presents a DNN-based method for identifying gas-bearing strata in tight sandstone. First, multi-component composite seismic attributes are obtained.The strong nonlinear relationships between multi-component composite attributes and gas-bearing reservoirs can be constrained through a DNN. Therefore, we identify and predict the gas-bearing strata using a DNN. Then, sample data are fed into the DNN for training and testing. After optimized network parameters are determined by the performance curves and empirical formulas, the best deep learning gas-bearing prediction model is determined. The composite seismic attributes can then be fed into the model to extrapolate the hydrocarbon-bearing characteristics from known drilling areas to the entire region for predicting the gas reservoir distribution. Finally, we assess the proposed method in terms of the structure and fracture characteristics and predict favorable exploration areas for identifying gas reservoirs.

The Influence of Acid on the RockMechanical Characteristics of Deep Shale in theWujiaping Formation

The microscopic characteristics and mechanical properties of rocks change after the action of acid on deep shale,which affects the fracturing effect.Accordingly,we designed and conducted indoor experiments related to the changes in macro and microscopic characteristics after the interaction of acid with the shale of Wujiaping Formation,based on which the characteristic law of fracture volume modification after acid fracturing was studied using numerical simulation.The results demonstrate that the pores and fractures are enlarged and the structure is significantly loosened after the acid immersion.And a 15%concentration of hydrochloric acid can effectively dissolve shale.Furthermore,the degree of acid-etching reaction is highly variable because of the different carbonate content,which reveals the strong inhomogeneity of the shale system in the Wujiaping Group reservoir section.After the acid interacted with the shale rock samples,the triaxial compressive strength,elastic modulus,and Poisson’s ratio of shale decreased.Moreover,the evaluation of the effect after acid fracturing simulated by fracturing software revealed that the smaller the value of elastic modulus in shale-based reservoirs,the more favorable the fracture volume modification.This discovery not only provides a theoretical basis for the expansion and extension patterns of acid-fracturing in carbonaceous shale formations but also offers research methods and theoretical insights for the fundamental exploration of other deep-seated oil and gas resources.

Formation of fractures in carbonate rocks by pad acid fracturing with different states of carbon dioxide

Carbonate outcrops were taken from Ma 51 sub-member in the Lower Paleozoic in the Yan’an gas field to conduct true tri-axial hydraulic fracturing experiments with water, liquid CO_(2) and supercritical CO_(2). CT scan was applied to analyze initiation and propagation laws of hydraulic fractures in carbonate rocks. The experiments show that supercritical CO_(2) has low viscosity, strong diffusivity and large filtration during fracturing, which is more liable to increase pore pressure of rocks around wellbore and decrease breakdown pressure of carbonate rocks. However, it would cost much more volume of supercritical CO_(2) than water to fracture rocks since the former increases the wellbore pressure more slowly during fracturing. For carbonate rocks with few natural fractures, tensional fractures are generated by fracturing with water and liquid CO_(2), and these fractures propagate along the maximum horizontal principal stress direction;while fracturing with supercritical CO_(2) can form shear fractures, whose morphology is rarely influenced by horizontal stress difference. Besides, the angle between propagation direction of these shear fractures near the wellbore and the maximum horizontal principal stress is 45°, and the fractures would gradually turn to propagate along the maximum horizontal principal stress when they extend to a certain distance from the wellbore, leading to an increase of fracture tortuosity compared with the former. For carbonate rocks with well-developed natural fractures, fracturing with fresh water is conducive to connect natural fractures with low approaching angle and form stepped fractures with simple morphology. The key to forming complex fractures after fracturing carbonate rocks is to connect the natural fractures with high approaching angle. It is easier for liquid CO_(2) with low viscosity to realize such connection. Multi-directional fractures with relatively complex morphology would be formed after fracturing with liquid CO_(2).

Efficacy and safety of tranexamic acid in elderly patients with intertrochanteric fracture: An updated meta-analysis

BACKGROUND Intertrochanteric fracture (ITF) is a common type of injury, and nearly 30% of ITF patients die in the first 12 mo, especially the elderly with limited activity. Tranexamic acid (TXA) has been widely used in reducing traumatic and surgical bleeding, however, the paucity of studies regarding its use in orthopedic trauma surgery has limited its integration into this field, which may benefit most from TXA. The safety of TXA in this group has not achieved a consensus. AIM This meta-analysis was designed to investigate the efficacy and safety of TXA in elderly ITF patients undergoing surgery. METHODS Databases, including Medline and PubMed, were searched for randomized controlled trials (RCTs) that were published before October 2018 and that addressed the efficacy and safety of TXA in patients who underwent ITF surgery. The Consolidated Standards of Reporting Trials 2010 Statement Checklist was used to assess the methodological quality of each study. Trials without and with heterogeneity were compared by fixed-effects analysis and random-effects analysis, respectively. For each study, odds ratio (OR) and 95%CI and mean differences and 95%CI were calculated for dichotomous and continuous outcomes, respectively. The Power and Sample Size Program software was used to calculate power and sample size. Stability of the results was assessed via sensitivity analysis. RESULTS A total of 836 patients from eight RCTs were subjected to meta-analysis. TXA treatment compared with the control group significantly reduced postoperative blood loss (95%CI,-20.83 to -7.93 mL, P < 0.0001), hidden blood loss (95%CI,- 213.67 to -64.43 mL, P = 0.0003), and total blood loss (95%CI,-332.49 to -23.18 mL, P = 0.02) by weighted mean differences of -14.38,-139.05, and -177.83 mL, respectively. However, no significant difference was observed between groups for analysis of intraoperative blood loss. The meta-analysis also proved that the usage of TXA in ITFs may not significantly increase the incidence of deep venous thrombosis. Allogeneic blood transfusion data showed that significantly fewer patients in the TXA group (42%) required transfusion than the control group (95%CI, 0.36 to 0.69;P < 0.0001). CONCLUSION In ITF surgery, intravenous administration of TXA reduces the risk of hidden blood loss and the need for allogeneic transfusion, without increasing thrombotic risk.

The Clinical Effect of Zoledronic Acid Combined with Teriparatide in Perverting Recurrent Fracture of Osteoporotic Vertebral Compressive Fractures in the Elderly after Percutaneous Kyphoplasty

Background: Zoledronic acid and teriparatide have been proved to be effective in improving bone metabolism and preventing fractures, but there is no clear clinical report on the efficacy of their combined application. Purpose: To discuss the clinical effect of zoledronic acid combined with teriparatide in perverting recurrent fracture of osteoporotic vertebral compressive fractures (OVCF) in the elderly after percutaneous kyphoplasty (PKP). Method: A randomized clinical trial was conducted at the First Affiliated Hospital of Hebei North University in China from September 2018 and September 2019. A total of 60 patients with OVCF were enrolled in the study (zoledronic acid: 20 cases;teriparatide: 20 cases;zoledronic acid + teriparatide: 20 cases). Observe and compare the changes of bone mineral density (BMD), pro-collagen type I N-terminal propeptide (PINP) and cross-linked C-terminal telopeptide of type I collagen (β-CTX) before surgery, 6 months and 1 year after surgery. At the same time, secondary fracture events and adverse reaction events were recorded during the follow-up period. Results: After normalized treatment, the bone metabolism indexes of PINP and β-CTX were improved and BMD was increased in three groups. Adverse Reactions: There was no statistical significance in the incidence of fever, gastrointestinal reactions and myalgia among the three groups (P > 0.05). The incidence of recurrent fractures in group A was higher than that in group C (P < 0.05), but there was no significant difference between group B and group C (P > 0.05). Conclusion: Zoledronic acid combined with teriparatide is superior to Zoledronic acid in preventing the risk of recurrent fracture after PKP for old patients with OVCF, but it has no significant advantage over teriparatide.

Risk of fracture and pneumonia from acid suppressive drugs

A recently published systematic review and meta-analy-sis, incorporating all relevant studies on the association of acid suppressive medications and pneumonia identi-fied up to August 2009, revealed that for every 200 patients, treated with acid suppressive medication, one will develop pneumonia. They showed the overall risk of pneumonia was higher among people using proton pump inhibitors （PPIs） [adjusted odds ratio （OR） = 1.27, 95% CI： 1.11-1.46, I2 = 90.5%] and Histamine-2 re-ceptor antagonists （H2RAs） （adjusted OR = 1.22, 95% CI： 1.09-1.36, I2 = 0.0%）. In the randomized controlled trials, use of H2RAs was associated with an elevated risk of hospital-acquired pneumonia （relative risk 1.22, 95% CI： 1.01-1.48, I2 = 30.6%）. Another meta-analysis of 11 studies published between 1997 and 2011 found that PPIs, which reduce stomach acid production, were associated with increased risk of fracture. The pooled OR for fracture was 1.29 （95% CI： 1.18-1.41） with use of PPIs and 1.10 （95% CI： 0.99-1.23） with use of H2RAs, when compared with non-use of the respective medications. Long-term use of PPIs increased the risk of any fracture （adjusted OR = 1.30, 95% CI： 1.15-1.48） and of hip fracture risk （adjusted OR = 1.34, 95% CI： 1.09-1.66）, whereas long-term H2RA use was not sig-nifcantly associated with fracture risk. Clinicians should carefully consider when deciding to prescribe acid-sup-pressive drugs, especially for patients who are already at risk for pneumonia and fracture. Since it is unneces-sary to achieve an achlorhydric state in order to resolve symptoms, we recommend using the only minimum effective dose of drug required to achieve the desired therapeutic goals.

Effect of α-lipoic acid combined with nerve growth factor on bone metabolism, oxidative stress and nerve conduction function after femoral fracture surgery

Objective: To discuss the effect of α-lipoic acid combined with nerve growth factor on bone metabolism, oxidative stress and nerve conduction function after femoral fracture surgery. Methods: A total of 110 patients with femoral fracture who received surgical treatment in the hospital between January 2015 and January 2017 were collected and divided into the control group (n=55) and study group (n=55) by random number table. Control group received postoperative nerve growth factor therapy, and study group received postoperative α-lipoic acid combined with nerve growth factor therapy. The differences in the contents of bone metabolism and oxidative stress indexes as well as the levels of nerve conduction function indexes were compared between the two groups before and after treatment. Results: Before treatment, the differences in the contents of bone metabolism and oxidative stress indexes as well as the levels of nerve conduction function indexes were not statistically significant between the two groups. After treatment, serum bone metabolism indexes BGP and PⅠNP contents of study group were higher than those of control group while CTX-Ⅰ and TRAP contents were lower than those of control group;serum oxidative stress indexes TAC, CAT and SOD contents of study group were higher than those of control group while MDA content was lower than that of control group;limb nerve conduction velocity SCV and MCV levels of study group were higher than those of control group. Conclusion: α-lipoic acid combined with nerve growth factor therapy after femoral fracture surgery can effectively balance osteoblast/osteoclast activity, reduce oxidative stress and improve limb nerve conduction velocity.

A critical review of self-diverting acid treatments applied to carbonate oil and gas reservoirs

Carbonate reservoirs generally achieved relatively low primary resource recovery rates.It is therefore often necessary to clean those reservoirs up and/or stimulate them post drilling and later in their production life.A common and basic carbonate reservoir cleanup technique to remove contaminating material from the wellbore is acidizing.The efficiency of acid treatments is determined by many factors,including:the type and quantity of the acid used;the number of repeated treatments performed,heterogeneity of the reservoir,water cut of the reservoir fluids,and presence of idle zones and interlayers.Post-treatment production performance of such reservoirs frequently does not meet design expectations.There is therefore much scope to improve acidizing technologies and treatment designs to make them more reliable and effective.This review considers acid treatment technologies applied to carbonate reservoirs at the laboratory scale and in field-scale applications.The range of acid treatment techniques commonly applied are compared.Differences between specific acid treatments,such as foamed acids,acid emulsions,gelled and thickened acid systems,targeted acid treatments,and acid hydraulic fracturing are described in terms of the positive and negative influences they have on carbonate oil production rates and recovery.Opportunities to improve acid treatment techniques are identified,particularly those involving the deployment of nanoparticles(NPs).Due consideration is also given to the potential environmental impacts associated with carbonate reservoir acid treatment.Recommendations are made regarding the future research required to overcome the remaining challenges pertaining to acid treatment applications.

深层碳酸盐岩储层酸压进展与展望

酸压改造是深层碳酸盐岩储层高效勘探开发的技术利器。随着勘探开发逐渐迈向特深层,厘清目前酸压技术发展现状与趋势至关重要。从酸压裂缝起裂与扩展、酸刻蚀水力裂缝与导流能力构建、酸压数值模拟技术3个方面阐释了酸压改造机理;分析了黏度控制型、生酸时间控制型、H+屏蔽吸附型、非盐酸基型等4类耐高温缓速酸液体系特点;系统梳理了我国深层碳酸盐岩酸压工艺技术发展的4个历程,剖析了目前9000 m以深特深层碳酸岩酸压面临的4个挑战:能否压开储层、地层温度突破酸液体系耐温极限、高温高压测试手段缺乏、储集体靶向沟通难度大。基于此,提出了5个酸压研究展望:特深井破裂压力精准预测、耐220℃多功能酸液体系研发、超高温高压实验平台构建、全在线酸压技术、超临界CO_(2)酸压技术探索,力求实现特深层碳酸盐岩高效立体开发。

延长氨甲环酸使用时间有助于减少老年股骨转子间骨折围术期隐性失血

背景:股骨转子间骨折好发于老年人,手术后会出现大量的隐性失血,减少隐性失血可以降低并发症和住院时间。目的:评估延长氨甲环酸的使用时间对股骨近端防旋髓内钉治疗转子间骨折围术期隐性失血的影响。方法:选择2022年1月至2023年5月自贡市第四人民医院经急诊收治入院的老年股骨转子间骨折患者共62例,均在牵引床上闭合牵引复位后置入股骨近端防旋髓内钉治疗。根据氨甲环酸的使用时间分为2组,对照组38例在切开皮肤前15-30 min给予氨甲环酸1 g静脉滴注,3 h后追加1 g;试验组24例在对照组的基础上,术后第1天再追加氨甲环酸1 g静脉滴注每12 h一次。术前、术后当天、术后第1,3,5天均复查血常规,统计血红蛋白量和红细胞压积,理论总失血量采用Gross方程计算,同时记录两组患者并发症发生情况。结果与结论:①通过统计学分析,两组患者术中显性出血量相差较小,差异无显著性意义(P>0.05);②试验组围术期血红蛋白下降量、总失血量、隐性失血量低于对照组,差异有显著性意义(P<0.05);③试验组术后第3天的血红蛋白值、术后第1,3天的红细胞压积值高于对照组,差异有显著性意义(P<0.05);④两组术后血红蛋白和血小板计数呈下降趋势,第3天的血红蛋白值为最低值,术后第1天的血小板值为最低值,然后开始回升;⑤两组患者术后并发症发生率相比差异无显著性意义(P>0.05);⑥结果表明,术后延迟氨甲环酸的使用时间,可能有助于减少股骨近端防旋髓内钉治疗股骨转子间骨折的隐性失血量,并不会增加并发症风险。

考虑采动效应的闭坑矿井水硫酸盐污染规律

高硫煤矿闭坑后成为埋藏在地表以下深部的产酸污染场,对相邻含水层和周边环境造成了潜在危害,且因采动效应影响和矿井空间分布复杂导致相邻含水层的污染过程与污染程度评价困难。以某闭坑矿区为研究对象,选取SO_(4)^(2-)作为特征污染物,考虑多煤层采动裂隙对含水层结构的破坏影响,运用数值模拟技术对闭坑矿区酸性矿井水中SO_(4)^(2-)污染迁移特征进行研究,并分析流体扩散系数对含水层污染物运移的影响。结果表明:SO_(4)^(2-)在二叠系童子岩组砂岩含水层中水平迁移面积随时间增大而增大,增大速率逐渐减小,垂向渗透系数扩大10倍,空间变异性增强;闭坑5、10、15a后,最大水平迁移距离分别为215、414、612m,最大垂向迁移距离分别达到50、65、70m;而扩散系数越大,产酸时间越长,SO_(4)^(2-)迁移距离和污染范围将随之增大,相较于水平方向,垂向上SO_(4)^(2-)浓度变化对扩散系数的敏感度更高。基于模拟结果,结合闭坑矿区实际条件,针对性提出了“源头减量-过程阻断-末端治理”的综合防控与治理方案。研究结果将为该闭坑煤矿酸性矿井水污染治理与防控提供理论基础,也为其他同类矿井提供科学借鉴。

基于“扩缝串洞”理念的超深层小缝洞群碳酸盐岩储层改造数值模拟

随着四川盆地和塔里木盆地碳酸盐岩油气藏勘探开发逐渐迈向超深层领域,受地质条件影响,储层由大型缝洞向以厘米—毫米级小缝洞群转变,以往针对大型缝洞储层改造的酸压技术系列难以适应小缝洞群储层。为充分释放超深层小缝洞群碳酸盐岩储层的天然气产能潜力,基于小缝洞群碳酸盐岩储层特征,构建了多尺度离散缝洞方法,建立了考虑岩石变形、裂缝延伸、酸液流动反应、温度变化的热流固化多场耦合数值模型,最后提出了以多级转向扩面积、精准控黏串缝洞、定点生酸扩缝长为核心的“扩缝串洞”缝控改造理念,并对小缝洞群碳酸盐岩储层“扩缝串洞”缝控改造方式进行了优化分析。研究结果表明:①多级交替注入形成的黏性指进现象可以促进缝控改造面积的增加和裂缝非均匀刻蚀,从而提高改造后的产能,且缝控改造效果最佳;②酸液注入黏度比增加,缝控改造无因次产能指数呈现先增大后减小的规律,当黏度比超过30,缝控改造无因次产能指数开始迅速减小,缝控改造中酸液交替黏度比需控制在25~35区间;③酸液用量越大,缝控改造面积及改造后无因次产能指数越大,但对于一定地层参数和单井控制面积的缝控改造存在极限酸液用量,超过该酸液用量后缝控面积趋于极限值,而无因次产能指数仍随酸液用量的增加而稳定增大。结论认为,提高缝控改造面积和激活动用小缝洞群是小缝洞群碳酸盐岩储层提产的关键,该认识为超深层小缝洞群碳酸盐岩气藏的高效开发提供了理论指导。

致密灰岩水平井复合缝网加砂压裂技术研究与矿场实践

鄂尔多斯盆地太原组石灰岩资源丰富,是长庆油田天然气勘探开发的重要接替领域。但由于储层致密、厚度薄、酸岩反应速率快等因素,以往多种酸压工艺均未能获得产量突破。为此,转变增产技术思路,强化裂缝扩展规律实验研究、压裂液及关键材料研发配套、体积压裂模式精细刻画,形成“多段少簇密集造缝、酸压—加砂双元复合”为一体的水平井复合缝网加砂压裂技术。通过开展大露头压裂物理模拟实验,结合储层地质特点及岩石力学特征,明确储层高脆性、低两向水平主应力差、微裂缝发育特征,采用体积压裂工艺能够实现复杂缝网改造;集“深度酸压+大规模加砂”双重技术优势,构建“水力缝网+酸蚀裂缝”相结合的高导流裂缝流动通道,结合水平井密切割压裂大幅提高裂缝改造体积;针对石灰岩高杨氏模量、高破裂压力、高裂缝延伸压力、低裂缝宽度的三高一低特征,通过提高套管承压等级、差异化裂缝铺砂设计,形成多尺度小粒径连续加砂模式,解决了高杨氏模量储层加砂难问题;基于基质、壁面、裂缝三级伤害评价,研发低伤害变黏滑溜水体系,实现高杨氏模量储层造缝、成网、携砂需求。现场试验4口井,平均单井产量为59.7×10^(4)m^(3)/d,较酸压直井提高5~20倍以上,增产效果显著。目前,水平井复合缝网加砂压裂技术已成为太原组石灰岩水平井储层改造的主体技术,为该类气藏的勘探突破及有效开发提供了有力的技术保障。

超临界CO_(2)对致密碳酸盐岩力学特性影响

采用超临界CO_(2)破致密碳酸盐岩具有破裂压力低,易形成复杂缝特点,但其作用的力学机理尚未清晰。选用马家沟组致密白云岩样,采用高温高压超临界CO_(2)饱和流体法,研究了岩样在超临界CO_(2)+地层水的流体中浸泡不同时间后的物性、声波响应、岩石力学特性和破裂形态特征。结果表明,随着浸泡时间增加,化学溶蚀作用引起溶蚀孔径增大,岩样孔隙度、渗透率增加,而声波速度、动态和静态岩石力学参数均下降;当浸泡时间大于1.0 d后,岩样物性参数增大和力学强度降低明显;随着浸泡时间增加,岩样破裂形态由单一低角度剪切缝向高角度剪切缝、共轭缝和剪切、张型复合缝等复杂形态发展;压裂短时间内(小于1.0 d)超临界CO_(2)+地层水形成的弱酸对岩石力学强度劣化程度有限。

灰岩酸蚀裂缝软化区域力学特性与微观特征

碳酸盐岩储层常采用酸化酸压工艺进行改造,酸蚀后岩石表面的微观结构被溶蚀破坏,岩石力学特性发生显著变化,进而影响最终的改造效果。为明确酸蚀对灰岩力学特性和微观孔隙结构变化的影响规律,开展了酸蚀前后灰岩力学特性实验、表面形态特征扫描电镜研究和微观孔隙结构核磁共振表征。结果表明,酸蚀后岩石表面出现了一定厚度的酸蚀软化层,厚度约为11.61μm。值得注意的是,由于酸蚀软化层的存在,灰岩抗压强度、弹性模量与表面硬度均降至酸蚀前的约40%。酸蚀后表层岩石内部产生了大小不一的溶蚀孔洞,并在溶蚀孔洞周边引发应力集中,改变了酸蚀软化层的应力分布。在高闭合应力作用下,溶蚀孔洞易于发生挤压变形或坍塌破坏,这也是酸蚀软化层力学性质改变的主要原因。结合核磁共振T2谱,发现孔径尺寸在1nm~1μm的孔隙数量变化最大,酸液溶蚀改变了灰岩软化层内部的孔隙结构,进而显著影响酸蚀后岩石的力学性质。

体外冲击波响应型唑来膦酸钙纳米颗粒靶向控释对骨质疏松骨代谢及骨量的影响

目的研究体外冲击波(extracorporeal shock wave,ESW)响应型唑来膦酸(zoledronic acid,ZOL)钙纳米颗粒(ZOL-Ca nanoparticals,ZCNP)的制备及其靶向控释对骨质疏松骨代谢及骨量的影响。方法通过模板法以ZOL为磷源,CaCl2为钙源制备ZCNP。利用扫描电子显微镜、动态光散射对ZCNP进行表征。通过紫外可见吸收光谱及电感耦合等离子体光发射光谱法评估ZOL的负载以及载药率。利用CCK-8法检测ZCNP对鼠源骨髓单核细胞(bone marrow mononu-clear cells,BMMs)活力的影响;采用溶血实验检测ZCNP的生物相容性。通过荧光标记ZCNP对其骨靶向性进行验证。采用药物释放实验验证了ZCNP的ESW响应性。在体外,利用TRAP染色检验ZCNP的破骨抑制情况;ARS染色检验ZCNP对成骨活性的影响。在体内,利用卵巢摘除骨质疏松模型验证ZCNP对骨量的影响。结果ZCNP呈类球形结构,约60 nm。ZCNP的ZOL负载率为(59.68±1.48)%。ZCNP在0、0.01、0.1、1、10μmol/L浓度下对小鼠BMMs的细胞活性影响无明显差异(P>0.05)。ZCNP在ESW作用下可快速释放ZOL。ESW+ZCNP可抑制破骨细胞活性,促进成骨细胞增殖。ESW+ZCNP可明显提高卵巢摘除骨质疏松模型局部骨量。结论ESW响应型ZCNP可通过有效精准靶向控释,抑制破骨,促进成骨提升卵巢摘除模型局部骨量,预防骨质疏松性骨折。

径向井辅助前置液酸压裂缝扩展数值模拟

基于扩展有限元及双尺度连续模型理论建立径向井辅助前置液酸压裂缝扩展模型,引入偏离系数作为量化评价指标,分析各因素对裂缝形态的影响,并利用灰色关联分析方法明确主控因素。结果表明:径向井对前置液酸压裂缝扩展具有显著引导作用,裂缝优先沿径向井方向起裂并扩展一定距离,而后逐渐偏向最大水平主应力方向;径向井方位角、水平地应力差和地层弹性模量越小,径向井长度越长,偏离系数越小,径向井引导效果越好,其中水平地应力差为主控因素;当径向井方位角为15°时,前置液酸压裂缝沿着径向井方向扩展14.32 m后偏向最大水平主应力方向,径向井的引导效果最好,偏离系数为0.005。

油气田酸化压裂环境下碳钢油套管材的腐蚀行为研究

为了明确某油田在酸化压裂环境下鲜酸、残酸对油套管材料腐蚀性能的影响规律及材料的适应性,采用腐蚀失重法、三维体视光学显微镜观察等方法分析了P110、C110油管材料在酸化全过程的腐蚀损伤发展趋势、点蚀敏感性和不同条件下的腐蚀形貌特征,并优化了酸化缓蚀剂。结果表明:随着鲜酸酸化温度的逐渐升高,材料腐蚀程度均呈增大趋势,当温度≥180℃时,C110的平均腐蚀速率v_(corr)=127.7 g/(m^(2)·h),P110的平均腐蚀速率v_(corr)=407.0 g/(m^(2)·h),均远高于指标要求;在模拟鲜酸温度为100℃时材料表面已出现点蚀形核现象,随着温度的升高,点蚀敏感性逐渐增大。在超高温180℃的残酸环境下,C110和P110材料均发生极严重腐蚀。酸化液组分中缓蚀剂在高温条件下明显失效,导致残酸返排环境下管材遭受严重腐蚀损伤。优化后的改性曼烯碱酸化缓蚀剂通过多层吸附膜的形成明显减缓了材料的腐蚀速率,在180℃高温鲜酸环境下缓蚀率为89.4%。

超深、特深碳酸盐岩多场-损伤耦合破裂压力计算

超深、特深碳酸盐岩储层破裂压力高,面临压不开的难题,酸液会与储层基质反应起到扩孔增渗以及劣化岩石力学性质的作用,进而降低破裂压力,但目前缺少碳酸盐岩储层酸损伤下的破裂压力精准计算方法,难以设计针对性的降破措施。针对上述问题,通过测试钻井液浸泡、酸液驱替后岩芯动态杨氏模量建立了不同流体扰动状态下的碳酸盐岩损伤演化方程,进一步建立了酸压过程中流动场、化学场和应力损伤场多场耦合的破裂压力数值计算模型,结果表明,钻井液酸液综合扰动条件下,孔隙度低于4.32%、酸化时间小于4.08 min时损伤因子小于0,无法解除钻井液污染导致的杨氏模量升高;P1井“井筒替酸+静止浸泡+浸泡后酸压”施工第73 min时8833m附近井段达到起裂条件,此时损伤因子为0.301,破裂压力降低了29 MPa,酸损伤降破后成功压开地层;模型计算结果与实测破裂压力误差为1%∼5%,较传统解析模型降低了3∼10个百分点,对于蓬莱气区灯影组或类似碳酸盐岩储层破裂压力计算与酸损伤降破措施设计具有一定指导意义。