Discovery and inspiration of large-and medium-sized glutenite-rich oil and gas fields in the eastern South China Sea:An example from Paleogene Enping Formation in Huizhou 26 subsag,Pearl River Mouth Basin

Based on the practice of oil and gas exploration in the Huizhou Sag of the Pearl River Mouth Basin,the geochemical indexes of source rocks were measured,the reservoir development morphology was restored,the rocks and minerals were characterized microscopically,the measured trap sealing indexes were compared,the biomarker compounds of crude oil were extracted,the genesis of condensate gas was identified,and the reservoir-forming conditions were examined.On this basis,the Paleogene Enping Formation in the Huizhou 26 subsag was systematically analyzed for the potential of oil and gas resources,the development characteristics of large-scale high-quality conglomerate reservoirs,the trapping effectiveness of faults,the hydrocarbon migration and accumulation model,and the formation conditions and exploration targets of large-and medium-sized glutenite-rich oil and gas fields.The research results were obtained in four aspects.First,the Paleogene Wenchang Formation in the Huizhou 26 subsag develops extensive and thick high-quality source rocks of semi-deep to deep lacustrine subfacies,which have typical hydrocarbon expulsion characteristics of"great oil generation in the early stage and huge gas expulsion in the late stage",providing a sufficient material basis for hydrocarbon accumulation in the Enping Formation.Second,under the joint control of the steep slope zone and transition zone of the fault within the sag,the large-scale near-source glutenite reservoirs are highly heterogeneous,with the development scale dominated hierarchically by three factors(favorable facies zone,particle component,and microfracture).The(subaqueous)distributary channels near the fault system,with equal grains,a low mud content(<5%),and a high content of feldspar composition,are conducive to the development of sweet spot reservoirs.Third,the strike-slip pressurization trap covered by stable lake flooding mudstone is a necessary condition for oil and gas preservation,and the NE and nearly EW faults obliquely to the principal stress have the best control on traps.Fourth,the spatiotemporal configuration of high-quality source rocks,fault transport/sealing,and glutenite reservoirs controls the degree of hydrocarbon enrichment.From top to bottom,three hydrocarbon accumulation units,i.e.low-fill zone,transition zone,and high-fill zone,are recognized.The main area of the channel in the nearly pressurized source-connecting fault zone is favorable for large-scale hydrocarbon enrichment.The research results suggest a new direction for the exploration of large-scale glutenite-rich reservoirs in the Enping Formation of the Pearl River Mouth Basin,and present a major breakthrough in oil and gas exploration.

Toxicity evaluation of produced formation waters after filtration treatment

During the last years many authors have char-acterized the produced formation waters (PFWs) with respect to chemical compounds and toxic-ity. Most of data are related to PFWs collected on offshore platform after treatment process. The available results showed that the particulate phase had an influence on PFW toxicity. As-suming the toxicity of PFWs treated on platform, the aim of this paper is to study the toxicity of these PFWs after a further filtration treatment carried out in laboratory. For this purpose PFWs were sampled from three natural gas platforms located in the Adriatic Sea (Italy) below treat-ment system. The eco-toxicological bioassays have been conducted on test-organisms be-longing to different trophic levels such as bac-teria, algae, crustaceans and fishes. The PFWs resulted toxic according to an overall assess-ment obtained through the bioassays. Further-more, it has been possible to identify the spe-cies that were more sensitive to the tested PFWs, namely Tigriopus fulvus, Dicentrarchus labrax and Vibrio fischeri. Besides, a chemical char-acterization was reported related to the con-taminants present in the PFWs to go with eco-toxicological assessment. Barium, zinc and manganese showed the most concentrations among the metals and the lower molecular weight components were common among the organic compounds. Some differences among PFWs were observed both for toxicity and chemical composition. The highest toxicity was recorded in PFWs (PFW1 and PFW2) containing the highest concentrations of some metals (Ba, Mn and Zn) and/or BTEX.

Experimental study on characteristics of pore water conversion during methane hydrates formation in unsaturated sand

Understanding the pore water conversion characteristics during hydrate formation in porous media is important to study the accumulation mechanism of marine gas hydrate.In this study,low-field NMR was used to study the pore water conversion characteristics during methane hydrate formation in unsaturated sand samples.Results show that the signal intensity of T_(2) distribution isn’t affected by sediment type and pore pressure,but is affected by temperature.The increase in the pressure of hydrogen-containing gas can cause the increase in the signal intensity of T_(2) distribution.The heterogeneity of pore structure is aggravated due to the hydrate formation in porous media.The water conversion rate fluctuates during the hydrate formation.The sand size affects the water conversion ratio and rate by affecting the specific surface of sand in unsaturated porous media.For the fine sand sample,the large specific surface causes a large gas-water contact area resulting in a higher water conversion rate,but causes a large water-sand contact area resulting in a low water conversion ratio(C_(w)=96.2%).The clay can reduce the water conversion rate and ratio,especially montmorillonite(C_(w)=95.8%).The crystal layer of montmorillonite affects the pore water conversion characteristics by hindering the conversion of interlayer water.

Experimental investigation of hydrate formation in water-dominated pipeline and its influential factors

Blockage in water-dominated flow pipelines due to hydrate reformation has been suggested as a potential safety issue during the hydrate production.In this work,flow velocity-dependent hydrate formation features are investigated in a fluid circulation system with a total length of 39 m.A 9-m section pipe is transparent consisted of two complete rectangular loops.By means of pressurization with gas-saturated water,the system can gradually reach the equilibrium conditions.The result shows that the hydrates are delayed to appear as floccules or thin films covering the methane bubbles.When the circulation velocity is below 750 rpm,hydrate is finally deposited as a“hydrate bed”at upmost of inner wall,narrowing the flow channel of the pipeline.Nevertheless,no plugging is observed during all the experimental runs.The five stages of hydrate deposition are proposed based on the experimental results.It is also revealed that a higher driving pressure is needed at a lower flow rate.The driving force of hydrate formation from gas and water obtained by melting hydrate is higher than that from fresh water with no previous hydrate history.The authors hope that this work will be beneficial for the flow assurance of the following oceanic field hydrate recovery trials.

Study of the Conditions of Formation and Forecast of the Perspective Areas of Hydrogen-Sulfide Water of Surkhandarya Depression

Increase in requirement of hydrosulphuric water for improvement of the population set the task of identification of places of their possible congestion for hydrogeological service. Earlier detection of such congestions was accidental at well-drilling of different function. Therefore, development of new methodical approaches of search and allocation of perspective zones of their formation was required. It was for this purpose necessary to study in what conditions and what factors have an impact on formation of underground hydrosulphuric water. So far, definition of communication attempts only with separate geochemical signs was known. Results of studying of influence on formations of hydrosulphuric water of such factors as lithologic and facial in combination with oil-and-gas content, the geological and structural and hydrodynamic mode are given in this work. It is established that the main sign for formation of hydrosulphuric water is existence of evaporite thickness and hydrocarbon congestions. Besides, it is shown that small depth (up to 2 km) of their bedding has to be an indispensable condition and existence of explosive violation on which there has to be a water infiltration (a geological and structural factor). In the Surkhandarya region, the hydrodynamic mode caused by inclined bedding of aquifers was also one of essential factors. Active water is an exchange process with washing away (oxidation) sulfate of the containing thicknesses and subsequently, its restoration in interaction with hydrocarbons with formation of hydrosulphuric water is described. The technique is developed and the expected card of perspective zones of formation of hydrosulphuric water is constructed.

The Degradation and Pollution of Soils on the Territory of the Kovykta Gas Condensate Field

In this paper, research results from the time interval 2002-2012 are used to give an account of the chemical composition of soils on the territory of the Kovykta gas condensate field. The findings presented provide a better understanding of the ecological state of soil cover, its resilience to anthropogenic impacts, and its possible disturbance caused by the drilling pad construction activity, and by the laying of geophysical profiles. An analysis of soil pollution for the study territory generally showed that the soils are polluted with chemical elements which refer to toxicity classes： Pb, Cu, Ni, Cr, Ba and Mn. High levels ofoil products were detected near boreholes. Strong mineralization was recorded in the soil near borehole. It has a chloride-sodium chemical composition. As a result of the construction of foundation pits, recesses, ditches and earth embankments, the soil is totally destroyed, and rock outcrops show up. Disturbances of the sod cover due to road construction or even by all-terrain vehicles in these extreme conditions entail an accelerated development of linear erosion to form scours and gullies. Elimination of the canopy layer leads to an increase in surface heating, and to an acceleration of permafrost thawing. Swamping is accelerated on negative relief forms due to the increased entry of melt waters.

Efficient development strategies for large ultra-deep structural gas fields in China

Through analyzing the development of large ultra-deep structural gas fields in China,strategies for the efficient development of such gas fields are proposed based on their geological characteristics and production performance.According to matrix properties,fracture development degree and configuration between matrix and fractures,the reservoirs are classified into three types:single porosity single permeability system,dual porosity dual permeability system,and dual porosity single permeability system.These three types of gas reservoirs show remarkable differences in different scales of permeability,the ratio of dynamic reserves to volumetric reserves and water invasion risk.It is pointed out that the key factors affecting development efficiency of these gas fields are determination of production scale and rapid identification of water invasion.Figuring out the characteristics of the gas fields and working out pertinent technical policies are the keys to achieve efficient development.The specific strategies include reinforcing early production appraisal before full scale production by deploying high precision development seismic survey,deploying development appraisal wells in batches and scale production test to get a clear understanding on the structure,reservoir type,distribution pattern of gas and water,and recoverable reserves,controlling production construction pace to ensure enough evaluation time and accurate evaluation results in the early stage,in line with the development program made according to the recoverable reserves,working out proper development strategies,optimizing pattern and proration of wells based on water invasion risk and gas supply capacity of matrix,and reinforcing research and development of key technologies.

Analysis of the world oil and gas exploration situation in 2021

The global exploration investment, new oil and gas discoveries, exploration business adjustment strategies of oil companies in 2021, and future favorable exploration domains are systematically analyzed using commercial databases such as IHS and public information of oil companies. It has been found that the world oil and gas exploration situation in 2021 has continued the downturn since the outbreak of COVID-19. The investment and drilling workload decreased slightly, but the success rate of exploration wells, especially deepwater exploration wells, increased significantly, and the newly discovered reserves increased slightly compared with last year. Deep waters of the passive continental margin basins are still the leading sites for discovering conventional large and medium-sized oil and gas fields. The conventional oil and gas exploration in deep formations of onshore petroliferous basins has been keeping a good state, with tight/shale oil and gas discoveries made in Saudi Arabia, Russia, and other countries. While strengthening the exploration and development of local resources, national, international, and independent oil companies have been focusing on major overseas frontiers using their advantages, including risk exploration in deep waters and natural gas. Future favorable exploration directions in the three major frontiers, the global deep waters, deep onshore formations, and unconventional resources, have been clarified. Four suggestions are put forward for the global exploration business of Chinese oil companies: first, a farm in global deepwater frontier basins in advance through bidding at a low cost and adopt the “dual exploration model” after making large-scale discoveries;second, enter new blocks of emerging hot basins in the world through farm-in and other ways, to find large oil and gas fields quickly;third, cooperate with national oil companies of the resource host countries in the form of joint research and actively participate exploration of deep onshore formations of petroliferous basins;fourth, track tight/shale oil and gas cooperation opportunities in a few countries such as Saudi Arabia and Russia, and take advantage of mature domestic theories and technologies to farm in at an appropriate time.

Prediction of wax precipitation region in wellbore during deep water oil well testing

During deep water oil well testing, the low temperature environment is easy to cause wax precipitation, which affects the normal operation of the test and increases operating costs and risks. Therefore, a numerical method for predicting the wax precipitation region in oil strings was proposed based on the temperature and pressure fields of deep water test string and the wax precipitation calculation model. And the factors affecting the wax precipitation region were analyzed. The results show that: the wax precipitation region decreases with the increase of production rate, and increases with the decrease of geothermal gradient, increase of water depth and drop of water-cut of produced fluid, and increases slightly with the increase of formation pressure. Due to the effect of temperature and pressure fields, wax precipitation region is large in test strings at the beginning of well production. Wax precipitation region gradually increases with the increase of shut-in time. These conclusions can guide wax prevention during the testing of deep water oil well, to ensure the success of the test.

姬塬油田注入水与地层水配伍性研究

姬塬长8储层在采用清水进行注水开发过程中,存在注水压力高、吸水指数低、注水见效慢、注采严重失衡等问题,严重影响油田开发效果。本文在对该区块注入水、地层产出水组成分析的基础上,将结垢趋势预测和室内模拟实验相结合,详细分析评价了注入水与地层水的配伍性。配伍性实验结果表明:姬塬长8储层地层水为CaCl2水型、注入水为Na2SO4水型;地层水与注入水以任意比例混合后,在30℃下均无垢生成,80℃下均产生了碳酸钙结垢而无硫酸钙垢形成。结垢趋势预测结果表明:在30℃下地层水与注入水混合后基本不生成碳酸钙垢;在50℃下,随着地层水比例的增加,碳酸钙结垢趋势增加,当地层水与注入水之比为4∶6 10∶0时,显示会有碳酸钙垢生成;在80℃下,碳酸钙垢趋势明显增加,地层水与注入水以任意比例混合后均会产生碳酸钙垢;在30℃、50℃、80℃下地层水与注入水以任意比例混合后均无硫酸钙垢结垢趋势存在。综上所述,姬塬长8储层注入水与地层水配伍性差、结垢是造成姬塬长8储层注水压力高的主要原因之一。

塔里木盆地哈得逊油田石炭系地层水化学特征及成因

塔里木盆地哈得逊油田石炭系地层水化学分析结果表明,地层水是以阴阳离子分别为Cl-和(Na++K+)为主的CaCl2型水,具有高矿化度特征(112～291 g/L)。地层水的钠氯系数均值为0.78,脱硫酸系数均值为0.23,Schoeller碱交换指数(IBE)均值为128。地层水化学参数在平面上相对变化不大,在剖面上随深度的增加,HCO3-、SO42-含量具有减小的趋势,而其他离子变化相对较小,表明研究区内的地层水形成于深部封闭环境条件下。地层水化学分析表明,该区地层水经历了强烈的阳离子交替吸附和水岩相互作用。(铁)白云石化作用导致了Ca2+的富集和Mg2+的亏损,形成了现今的地层水离子分布特征。石炭系地层水在构造反转油气藏调整时期一直处于相对封闭的流体动力环境中,这种环境有利于油气的聚集与保存。

川西地区上三叠统气田水化学场特征

以水文地质和与其关联的第一性资料入手 ,研究了川西地区上三叠统气田水化学参数的基本特征以及正向、斜向垂直水化学分带性 ,并结合油气研究成果和气田分布现状 ,对川西坳陷的含油气性和气田保存条件进行了水文地质评价和预测。研究表明 :本区存在三种水化学斜向垂直分带变化类型 ,即正向型、正向—反向型、正向—反向交替型 ;川西坳陷南部的灌口—平落坝断褶带和大兴鼻状构造带为天然气富集的最有利水文带。

哈得4东河砂岩油藏注水水质标准研究

塔里木哈得4东河砂岩油藏将由注矿化度25 g/L的地表水(清水)转为注矿化度240 g/L的采油污水。清水与污水配伍性差,应分注,注清水时需采取防垢措施。实验考察了与注入水腐蚀性、地层伤害性有关的诸因素,推荐了清水和污水水质控制指标。要将A3钢在清水和污水中的腐蚀率控制在0.076 mm/a以内,溶解氧浓度均应小于0.89 mg/L(尽管污水对溶解氧的耐受性强),TGBI、B、SRB菌数应分别小于103、102、102个/mL。根据储层岩心注模拟水伤害实验结果并考虑油田生产情况,为了使储层岩心渗透率的伤害率低于15%,注入水(清水、污水)中悬浮物粒径应控制在5μm以下,悬浮物含量小于7.5 mg/L,TGBI、B、SRB菌数应分别小于104、103、102个/mL,Fe3+浓度应小于2 mg/L,含油量应小于10 mg/L。图11参6。

胜利油区砂岩储集层敏感性特征研究

通过 50个油田 180 0余块样品的敏感性试验研究 ,运用胜利油区Ng、Es1、Es2 、Es3、Es4 等 5个砂层组的储集层敏感性室内实验资料 ,结合各油田储集层特征 ,总结胜利油区不同层位、不同埋深砂岩油藏的储集层敏感性特征及油层损害机理 ,认为 :水敏性是该油区储集层的主要敏感性损害因素 ;流速过大会导致疏松砂岩储集层出砂 ;储集层具有弱—中等的碱敏性 ;对于盐酸和土酸表现出不同的敏感性结果。

低自由水钻井液体系的研究与应用

为了解决南堡油田玄武岩井壁失稳和储层保护问题,研究了低自由水钻井液体系。该钻井液体系通过对自由水的络合,增大了钻井液进入地层的毛管阻力;通过润湿剂降低地层岩石的毛细管自吸水能力;通过封堵地层裂隙、改善泥饼质量,提高井壁的承压能力;该钻井液体系一方面可实现低密度安全钻穿玄武岩,提高油层保护效果,另一方面为简化井身结构打下基础,可进一步提高钻井速度并降低钻井费用。通过在南堡13-斜1064井现场的成功试验,实现了同一裸眼井上部玄武岩井壁稳定和下部储层保护的双重目的,为安全钻进和储层保护提出一个新理念。

东营凹陷古近系古湖盆演化与水化学场响应

东营凹陷古近系水化学场分布与湖盆演化有着良好的对应关系,以CaCl2水型为主的高矿化度地层水是东营凹陷古近系咸化湖盆的典型响应特征,矿化度从深到逐渐降低,体现出从咸化湖盆向微咸化湖盆及淡水湖盆演化的地球化学响应.剖面上可以划分为四种水文环境:强开放性水文流畅带(地表到1.1km)、弱开放性水文流畅带(1.1-2.0km)、水文阻滞过渡带(2.0-2.5km)和封闭性水文迟缓带(2.5km以下),水化学剖面的分带性与压力分布有着良好的对应关系.东营凹陷古近系水化学场经历了早期的沉积与淋滤的交替和新生代的埋藏封闭作用期,其中在东营运动时期古近系水化学场表现最为活跃,是深层卤水咸化地表浅层淡水从而使浅层出现高矿化度地层水的关键作用期,断裂的沟通起了重要作用,显示出断陷湖盆的典型特征.

榆树林油田注水井结垢及其机理研究

大庆榆树林油田注水井及其配套系统结垢严重。本文报道了对结垢及其机理进行研究的结果。注入水易结垢，垢主要由ＣａＣＯ３组成（占９２．５％），井筒内结垢量达４６％，其余垢沉积在井底和地层内。讨论了流动状态、温度、压力、地层水等因素对ＣａＣＯ３从注入水结晶析出及沉积的影响。

适于高矿化度地层水地层的稳油控水绒囊流体

为验证绒囊流体在含高矿化度地层水地层中稳油控水效用,在温度120℃、围压15 MPa、回压1.5 MPa条件下,采用恒流速法测定绒囊流体封堵前后,含不同矿化度盐水和煤油的人造砂岩柱塞稳定流动渗透率和注入压力变化。实验结果表明,0.1 m L/min恒定流速下,绒囊流体封堵前后,含Fe2＋＋Ca2＋＋Mg2＋矿化度分别为1×104 mg/L、10×104 mg/L、20×104 mg/L盐水岩心驱替压力由0.46~0.63 MPa升至1.39~2.23 MPa,封堵能力提高205.83%~262.64%;渗透率140.82~193.30 m D降至66.96~109.85 m D,损失率43.15%~52.53%。以煤油模拟地层原油,相同条件下测定封堵前后效果,驱替压力0.48~0.52 MPa升至0.51~0.55 MPa,增幅5.83%~8.08%;渗透率232.05~272.52 m D降至211.09~249.25 m D,损失率2.26%~4.51%。在地层水矿化度8×104 mg/L、4×104 mg/L的Y井和Z井实施绒囊流体稳油控水,通过提高泵次、深抽等工艺,油井产水量分别降低46.38%、15.99%,产油量提高6 200%、180%。研究和应用表明,绒囊流体抗高矿化度堵水体系能够实现稳油控水。

塔里木盆地塔河油田水离子组合及参数的平面分布与油气运移

通过对塔河油田水离子组合及其参数的平面分布图的编制来推断油田水系统的形态、分布,并根据其参数变化梯度分析了油气运移方向。研究表明:塔河油区油田水参数的平面分布总体具有南北分块、东西分带的特征;其中,塔河1、2区三叠系油田水主要呈东西向分布,而塔河3、4、6区具有南北条状带向分布,但东西分异、南部平台区则为近东南-北东-南西向分布;7区西北部和8区可能呈南北向分布。同时,油田水分布局部呈洞穴状、桶状和其它不规则孤立或封闭流体系统;出现水动力相对强或弱的交替带或滞后区带;其离子及组合参数均指示油气运移的主导方向是自南、西南向北、北东方向。

宝浪油田注水结垢趋势预测及试验验证

针对宝浪油田水化学特点 ,应用 Skillman和 Odd-Tomson方法分别预测硫酸钙垢、碳酸钙垢的结垢趋势 ,通过静态结垢试验证实了理论预测结果。研究结果表明 ,宝浪油田注水结垢只可能产生碳酸盐垢而不会产生硫酸钙垢 ;结垢成因是由于系统内的热力学不稳定性引起的 ,即注入水温度、p H值升高或地层内CO2 分压降低都会导致结垢。