Henan Oilfield Research Articles

Evaluation of Profile Control and Oil Displacement Effect of Starch Gel and Nano-MoS2 Combination System in High-Temperature Heterogeneous Reservoir.

The Henan Oilfield's medium-permeability blocks face challenges such as high temperatures and severe heterogeneity, making conventional flooding systems less effective. The starch gel system is an efficient approach for deep profile control in high-temperature reservoirs, while the nano-MoS2 system is a promising enhanced oil recovery (EOR) technology for high-temperature low-permeability reservoirs. Combining these two may achieve the dual effects of profile control and oil displacement, significantly enhancing oil recovery in high-temperature heterogeneous reservoirs. The basic performance evaluation of the combination system was carried out under reservoir temperature. Displacement experiments were conducted in target blocks under different permeabilities and extreme disparity core flooding to evaluate the combination system's oil displacement effect. Additionally, the displacement effects and mechanisms of the starch gel and nano-MoS2 combination system in heterogeneous reservoirs were evaluated by simulating interlayer and intralayer heterogeneity models. The results show that the single nano-MoS2 system's efficiency decreases with increased core permeability, and its effectiveness is limited in triple and quintuple disparity parallel experiments. After injecting the starch gel-nano-MoS2 combination system, the enhanced oil recovery effect was significant. The interlayer and intralayer heterogeneous models demonstrated that the primary water flooding mainly affected the high-permeability layers, while the starch gel effectively blocked the dominant channels, forcing the nano-MoS2 oil displacement system towards unswept areas. This coordination significantly enhanced oil displacement, with the combination system improving recovery by 15.33 and 12.20 percentage points, respectively. This research indicates that the starch gel and nano-MoS2 combination flooding technique holds promise for enhancing oil recovery in high-temperature heterogeneous reservoirs of Henan Oilfield, providing foundational support for field applications.

Evaluation of viscosity reduction effect of oil-soluble viscosity reducer on crude oil

In this paper, several crude oil viscosity reducers were selected to evaluate their performance on the heavy oil Henan Oilfield, China. Through investigation, the viscosity reducing ability of these viscosity reducers were relatively general. Among them, EVA had the highest performance, reaching a viscosity reduction rate of 45.6%. The results were characterized by DSC analysis, wax crystal micromorphology analysis of saturated hydrocarbons and IR spectroscopy. Finally, possible viscosity reduction mechanism was discussed.

Experimental Study on Blockage Mechanism and Blockage Locations for Polymer-Flooded Reservoirs in the Henan Oilfield

To address the issues of reservoir blockage and sharp decline in fluid output of production wells in the polymer injection zone of the Henan oilfield, physical modeling has been used to study the blockage mechanism and blockage locations of the polymer-flooded reservoir based on oil reservoir characteristics and blockage knowledge. The results show that all the constant pressures in the low, moderate, and high permeability cores subjected to polymer injection and subsequent waterflooding were higher than the constant pressure during primary waterflooding; hence, polymer retention and blockage phenomena were obvious in the cores; in the high permeability core, the pore surface adsorbed more polymer molecules though pore throat radii were still much greater than the size of the polymer molecule, suggesting that polymer blockage is mainly caused by adsorption and retention. For the low permeability core, the specific surface area of the inlet end was much larger than that in the high permeability core, leading to more serious capture of polymer molecules at the small pores, indicating that blockage under polymer injection is mainly caused by capture and retention; for the lower permeability (91.81 mD) core, as compared with the case prior to polymer injection, the polymer-injected core had fewer large pores and throats, the mean pore throat radius decreased from 42.2 μm to 39.9 μm, and the mean throat-to-pore coordination number decreased from 3.36 to 3.19; thus, polymer capture and retention led to core blockage; the leftward shift of the curve corresponding to the porosity component, high porosity peak weakening after polymer injection, moderate and low porosity peaks appearing after polymer injection, and enhancement of lower porosity peaks indicate that, after polymer injection and subsequent waterflooding, polymer adsorption and capture led to blockage of some large pores; the highest pressure gradient, i.e., 6.3 MPa/m, was achieved at the P2-P3 segment; thus, the worst blockage occurred at the P2-P3 stage, or 1/8-1/4 of the sandpack length. In this paper, Nanbaxian oil and gas field, China, was taken as an example to investigate the interpretation method of gas saturation in a complex pore structure. The “four properties” relationship of the formation reservoir in the Nanbaxian oil and gas field was studied in depth according to the conventional logging data and core analysis data. The neural network algorithm was used to reconstruct the resistivity curve of the water layer to eliminate the influence of lithology, shale content, and pore structure on the resistivity. The difference between the reconstructed curve and the measured resistivity curve was used to identify the gas and water, and the ratio of the two was used to calculate the gas saturation, and good results were achieved. It was found that the sedimentary types of the Nanbaxian oil and gas field cause the reservoir to be thin, numerous, and dispersed; the lateral correlation is difficult. In addition, the structural features lead to the reservoir types being various in the vertical direction, which makes the identification of reservoir fluid more difficult. The results revealed that the rock compaction, poor physical properties, complex pore structure, high resistivity of surrounding rocks, and low formation water salinity make the water layer with high resistivity and difficult to identify gas and water.

Characterization of compositions in crude oil and the effect of inhibitor on the crystallization of paraffin

Flowability is one of the important characters of a crude oil in pipelines. The viscosity of one crude oil is affected by many factors (e.g., temperature, water cut, composition distribution, paraffin deposition, etc.). In this study, IR, thermogravimetry analysis (TGA) and UV measurement are employed to characterize the composition of the crude oil (HN-1) provided by Henan Oilfield. The paraffin morphology analysis is employed to rate the property of a mixture of paraffin inhibitors and analysis the mechanism of the paraffin inhibition.

FRACTAL CHARACTERISTICS OF CONTINENTAL SHALE PORES AND ITS SIGNIFICANCE TO THE OCCURRENCE OF SHALE OIL IN CHINA: A CASE STUDY OF BIYANG DEPRESSION

Samples from seven major exploration wells in Biyang Depression of Henan Oilfield were compared using low-temperature nitrogen adsorption and shale oil adsorption experiments. Comprehensive analysis of pore development, oiliness and shale oil flowability was conducted by combining fractal dimension. The results show that the fractal dimension of shale in Biyang Depression of Henan Oilfield was negatively correlated with the average pore size and positively correlated with the specific surface area. Compared with the large pore, the small pore has great fractal dimension, indicating the pore structure is more complicated. Using S1 and chloroform bitumen A to evaluate the relationship between shale oiliness and pore structure, it was found that the more heterogeneous the shale pore structure, the higher the complexity and the poorer the oiliness. Clay minerals are the main carriers involved in crude oil adsorption, affecting the mobility of shale oil. When the pore complexity of shale was high, the content of micro- and mesopores was high, and the high specific surface area could enhance the adsorption and reduce the mobility of shale oil.

ASP Flooding: Theory and Practice Progress in China

In low oil price era, it seems that ASP flooding has little market. However, ASP progress in China shows that ASP flooding is good technology to help oil companies thrive and make profit. Since 2014, ASP flooding has entered industrial application in Daqing oilfield. ASP flooding production in 2015 is 3.5 million ton, 9% of the oilfield’s total production of Daqing oilfield. There are 22 ASP flooding blocks in Daqing, containing 7231 wells and 3 are new blocks in 2016. Obviously, more and more ASP flooding is being carried out. Another large ASP flooding field test in high temperature (80°C) in Henan oilfield has got staged incremental oil recovery of 7.7%. Latest theory and application in ASP flooding in China are reviewed to help ASP flooding go from success to more application. Weak alkali is better than strong alkali ASP flooding. Relation between viscosity and IFT is discussed. This paper also explains why weak alkali ASP flooding is promoted in Daqing after 12 field tests on strong alkali one. ASP flooding can be a great help to survive low oil price.

Treatment Technology on Polymer Flooding Wastewater in Henan Oilfield

Polymer flooding has became one of the most important oil recovery technologies with Chinese oilfields coming into tertiary recovery, which lays a solid foundation for high and stable yields in oilfields. But with it’s large-scale industrial production, polymer flooding technology also brings difficulties for the disposal and treatment of polymer flooding wastewater. Compared with conventional water flooding wastewater technology, polymer flooding wastewater not only contains oil but also lots of polymer. “Old three sets” process cannot meet the national discharge standard or the injection water quality standard. Relied on HeNan oilfield united station, this paper studied on the treatment of polymer flooding wastewater, a kind of efficient flocculant was selected for the treatment of polymer flooding wastewater and a set of reasonable technological process was recommended, making the wastewater after disposal meet the injection water quality standard.

河南油田95℃油藏用聚合物评价与应用

为保证河南油田VII1-3层系高温油藏聚合物驱先导试验的成功，项目在室内系统评价了聚合物性能及聚合物与油藏配伍性能。配制水质、溶液中溶解氧含量、剪切、高温老化等都影响高温聚合物溶液粘度。特别是溶液中溶解氧含量对聚合物粘度长期热稳定性影响显著。氧含量对水解度影响不大。溶解氧含量小于0.5 mg/L条件下，聚合物在95℃高温下老化90天后，结构具有一定的稳定性，拉伸流变稳定性和剪切流变稳定性，老化180 d后粘度保留率可达到80%以上。渗透率为油藏渗透率0.587 μm2，聚合物浓度在1000 - 2000 mg/L范围内，具有较好的注入性。进入矿场应用后，聚合物现场注入性良好，已取得明显的增油降水效果。 In order to ensure the success of polymer flooding pilot test in Henan oilfield VII1-3 formation high temperature reservoir, a lot of tests are researched about the performances of the polymer and its compatibility with the reservoir in the laboratory. These factors influence on the viscosity of polymer solution including water quality, dissolved oxygen content in waste water, shearing, high temperature aging, etc. Especially the dissolved oxygen content in the solution has a great effect on the long-term thermal stability of polymer viscosity. Oxygen content has a little effect on the degree of hydrolysis of polymer. When the dissolved oxygen content is less than 0.5 mg/L, the structure, tensile rheological and shear rheological performance has certain stability in 95˚C high temperature aging 90 days. Aging viscosity retention rate can reach more than 80% after 180 days. It has a good injection within the range 1000 - 2000 mg/L of polymer concentration, when the permeability is 0.587 μm2 of the reservoir. After entering the field application, the polymer injection is good. It has obvious effect of enhanced production of oil and water cut.

Enhanced foam stability by adding comb polymer gel for in-depth profile control in high temperature reservoirs

Abstract A long-term stability of gel enhanced foam as an in-depth profile control agent in high temperature reservoirs was successfully prepared by adding comb polymer gel. The increased viscosity of gel brings a negative effect on surface tension which reduces the gel enhanced foam volume. In turn, the increased viscosity could enhance the thickness and strength of foam film which increases foam stability and plugging capacity in porous media. The morphology results show that the gel enhanced foam has a thicker bubble film which enhances its foam stability. The effect of injection mode, gas–liquid ratio, gas injection velocity and formation permeability on the plugging capacity was investigated by single sand-pack experiments. When the gas–liquid ratio and gas injection velocity were respectively set at 1:1 and 0.5 ml/min, co-injection of gel enhanced foaming solution and gas could obtain a better plugging capacity in high permeability sand-packs. Parallel sand-pack experiments show that the profile improvement capacity of high formation permeability ratio is much better than that of low formation permeability ratio. The visual simulation experiment was also conducted to illustrate the flowing behavior of gel enhanced foam. By Jiamin effect or Jamin superimposed effect, directly plugging and bridging in the large pore space, the gel enhanced foam can effectively reduce the permeability of porous media in high permeability zones and divert fluid into low permeability zones, thus increases the swept volume. The treatment has been successfully used in Henan oilfield of China which provides a reference to water production control in other similar high temperature oilfields.

Application of Polymers in Low Permeability Formations

For low-permeability sandstone reservoir with big channel, we researched the novel deep profile method alternative injection of anionic and cationic polymer. Evaluating various factors on adsorption capacity through lab test, the results show that with the increase of temperature, the adsorption capacity decreases and the cationic polymer is easier to be absorbed. With the increase of salinity, adsorption time or polymer concentration, the adsorption capacity increases. The adsorption equilibrium concentration of cationic polymer is 1500 mg/L; adsorption equilibrium time is 8 h. The adsorption equilibrium concentration of anionic polymer is 1000 mg/L; adsorption equilibrium time is 6 h. Physical simulation experiment shows that alternative injection of anionic and cationic polymer is better than injection of single polymer, and preferential injection of cationic polymer is better than preferential injection of anionic polymer. With the increase of injection rounds, sealing capacity gets better, but in view of cost, the rounds should not be more than 3. The profile control technique can obviously enhanced oil recovery, and water displacement recovery increases 41%. 2 wells were tested successfully in Henan Oilfield in June 2010. Approximate 154.47 tons of incremental oil was obtained with 2% water-cut decrease.

Study on Oil-Water Interfacial Behaviour of Henan Oilfield

In order to decide the formula of ASP system to be used in Henan oilfield, the weak base ternary composite system compounded with petroleum sulfonate(Ss), polymer and weak base; the alkali ASP system compounded with alkylbenzene sulfonates(Sy), polymer and alkali were studied, and the oil-water interface behaviour of Henan oilfield with weak base ASP system compounded with surfactant SHSA-HN6 and ZL-Ⅱ polymer was evaluated. The results showed that the interfacial tension reduction effect of Weak base ternary system is better than that of Alkali ternary system; the interfacial tension between oil and water can be reduced significantly by the weak base ternary system compounded with surfactant (Ss) and polymer (ZL-Ⅱand KYPAM). After adding 1.2% Na2CO3 to the mixture of surfactant (SHSA-HN6) and polymer, the interfacial tension of Henan oil-water was reduced to the ultra-low level(>10-3mN/m).

Application of Ultra-Heavy Oil Well Completion Technique in Heat Insulated Casings

The best is to read these instructions and follow the outline of this text. To improve the injection steam enthalpy is the key technology in ultra-heavy oil thermal development. The wellbore heat insulation technology is needed to keep the process of steam injection hot enthalpy, to reduce heat loss utmost, to prevent the damage of the casings and cement mantle in high-temperature steam. The conventional cased-hole completions require the borehole thermally insulating insulation technology in thermal recovery, and generally adopt insulated tubing steam injection, ordinary tubing transfer pumping, which will cause frequent operations and enlarge the accidental risks caused by a number of down hole tools which are tripped in wellbore. Insulation casing well completion technology can effectively solve the wellbore insulation problems, and improve the casing and cement mantle security, increase the production rate. The field applications in Henan Oilfield have obtained excellent results; two wells were operated with completion technique by heat insulated casings. Compared with the same types of wells in the pilot test ultra-heavy oil block, the production is about twice as much as those of other wells, and the economic effect is obvious.

Evaluation of the dynamic sealing characteristics of gel in Henan oilfield

Evaluation of the dynamic sealing characteristics of gel in Henan oilfield

Study of Development of Medium-Deep Heavy Oil Reservoir Pilot Tests in Henan Oilfield

Henan Oilfield Xiaermen Qianbei block is the medium-deep heavy oil reservoir. Due to the high viscosity of crude oil, formation cementation loose, sand production and reservoir water-sensitive, the pre-trial is less effective. The problem is the inefficiency of steam injection, poor oil-steam ratio, sand production serious, the poor pump efficiency and the abnormal productions. It is important to improve the mobility of heavy oil in the formation and wellbore for the development. According to the reservoir characteristics and the experience of the primary development, the measures which include the high-pressure gravel packing sand control, insulated tubing of steam injection, anti-swelling agent reservoir protection, formation and wellbore viscosity reducer and rod sucker-rod pumping system are carried out in a pilot test of the four wells. After the pilot test, the oil-steam ratio increases from 0.08 to 0.55, the average daily oil production increases from 0.5 tons to 8.0 tons. The pilot test has achieved great success and promoted the application in medium-deep heavy oil thermal recovery in the entire block, simultaneously provided the basis for the efficient development of other similar blocks.

Quantitative description of steam channels after steam flooding

Steam channeling is one of the main barriers for EOR after steam flooding. In order to enhance the oil recovery in steam flooded reservoirs, steam channel volumes should be precisely known. In this paper, a set of methods has been established in order to study steam channeling quantitatively by using dynamic data. Firstly, steam channeling wells are identified through curves of watercut and temperature. Then, considering the hysteresis phenomenon, channeling relations are identified with the correlation coefficients between injection wells and production wells under different conditions. Lastly, an analytic model, in which steam condensation, pressure and temperature are considered, is established to calculate the steam channel volumes. A production well named L31615 in some block in Henan Oilfield in China is systematically analyzed by using the method established. The whole block is further analyzed, and the distribution map of steam channels and the steam channel volumes are obtained. The results show that steam channeling does not only occur inside a well group, but also sometimes occurs between wells in different well groups. The calculation of the steam channel volumes provides a theoretical basis for bringing a remedial action like plugging into operation.

Research on Removal of SiO<sub>2</sub> from Heavy Oil Wastewater

For heavy oil wastewater from Henan oilfield, removal of silica has been investigated under the condition of different flocculants and reaction time when magnesia has been used as a desilica agent. An optimum method has been determined by conditional experiments, 63% of silica could be removed.

Calculation Method of Treatment Radius about Water Plugging for Layered-Parallel Beds Model

Profile control/water plugging is an important approach to increase production. Reasonable treatment radius and the volume of blocking agent are essential parameters not only in profile control/water plugging engineering but also in the area of reservoir simulation. Traditional calculation method used for treating layer only is derived by Darcy's equation. However, traditional calculation method neglect the influence of multilayer characteristics, which may lead to erroneous results. In this research, a new calculation method about profile control/water plugging is derived by considering the influence of multilayer characteristics. In order to derive this equation, layered-parallel beds model is established and ideal Darcy's radial flow theory is applied. In the new calculation method, treatment radius depends on desired effects, water plugging effect and multilayer characteristics. The scheme proposed by using the new calculation method is evaluated by using data from block SH2 in the HeNan oilfield. Calculation results show that the variation of treatment radius is generally in good agreement with actual situation.Introduction.

Using Biological Treatment of Henan Oilfield -Produced Water: Pilot Plant Test Study

Biological treatment of heavy crude oil production wastewater is well-established method for remediation of these wastes. We have developed effective biological treatments by (1) utilizing microbes with high oil-degrading abilities, (2) allowing greater organic loads while increasing both process stability and the resistance to shock loading, (3) minimizing the production of waste sludge byproducts, and (4) adopting anaerobic and aerobic biological processes to improve the biodegradation of the wastewater. Fixed-film bioreactors with 15h hydraulic retention times have decreased chemical oxygen demand by 74.8%, total suspended solids by 90.9%, oil by 80.6%, and phenols and sulfides by 100%. The results with an in situ pilot system show that the bioreactor's hydrolytic acidulation and contact oxidation tanks are suitable for treating oilfield wastewater, and that water quality after treatment fully meets national drainage standards.

Technical Principle of Integrated Solidification and Cementation at Cement-Formation Interface with Mud Cake to Agglomerated Cake (MTA) Method and its Oilfield Application

The technical principle of integrated solidification and cementation at cement-formation interface (ISCCFI) with Mud Cake to Agglomerated Cake (MTA) method based on the mud cake modifier and forming agent of agglomerated cake can be divided into two steps. Firstly, add the mud cake modifier (the amount is 1 % to 3 %) to the drilling fluid before drilling the isolation section, and keep this proportion until the well completion. Secondly, prepare 3 to 4 cubic meters of prepad fluid based on forming agent of agglomerated cake before the well cementing operation. This new method doesn’t need to change oilwell cement slurry system. In order to verify the practical cementing effect of MTA method, it was applicated in 16 adjustment wells (9 conventional wells and 7 heavy oil wells) in the old area of two oilfields in China. The interpretation results of CBL/VDL (Cement Bond Logging/Acoustic Variable Density logging) show that the qualified rate of casing-cement interface and cement-formation interface is up to 100 %, and the qualified rate of cement-formation interface increased by 30 % in Shengli oilfield and the average high-quality rate of all the isolation section length at cement-formation interface reaches 90.48 % in Henan oilfield.

Study and Application on Reutilization Technology of Residual Polymer After Polymer Flooding

There is a large amount of residual polymer existing in the forms of solution, adsorption, and entrapment in formation after polymer flooding. Then the water cut ascends quickly along high permeable channels when displacing water. In order to improve sweep efficiency of water flooding and use residual polymer effectively in formation, the reutilization technology of residual polymer in formation is proposed and developed. When the reutilization agents (including a flocculating agent and fixed agent) are injected, they react with residual polymer to form floc units and cross-linking units that could block high permeability channels and control cross flow. As a result, the sweep efficiency of water flooding and oil recovery could be enhanced. In this article, the optimized flocculating agent is selected through suspension experiments and the fixed effect for polymer is studied in sand pack core models, and the residual resistance factor is used as the evaluation criterion. The experiments show that solid particles can be used as a flocculating agent and the optimal flocculating agent is stabilized sodium clay; the cross-linking agents can be used as a fixed agent and the optimal fixed agent is selected depending on formation temperature and the salinity. This technology has been successfully applied in Henan oilfield, Shengli oilfield, and Daqing oilfield. The water cut and produced polymer concentration decreases dramatically and oil production increases obviously. This technology, which belongs to quaternary oil recovery technology, is a preferred improved oil recovery technology after polymer flooding and has a broad application prospect.