可降解顆粒包括在用于地下應(yīng)用如鉆井中能進行不可逆降解的可降解材料(其通常是可降解聚合物)。此處所使用的術(shù)語"一種顆粒"或"多種顆粒"是指具有以下物理形狀的一種或多種微粒薄層(platdet)、刨花(shavings)、纖維、小薄片(flake)、帶狀、棒、條、球體、超環(huán)狀、小球狀、片(tablet)或其它合適形狀的。作為此處所使用的術(shù)語"不可逆，，意指可降解材料可原位降解(例如在鉆井中)，但降解之后不會原位(例如在鉆井中)重結(jié)晶或重新固結(jié)。術(shù)語"降解"或"可降解"指可降解材料可以進行諸如異相(或本體消耗)和均相(表層消耗沐解降解的兩種相對極端情形，以及在這兩者之間的任意降解階段。

Degradable particles include biodegradable materials (usually biodegradable polymers) that can be irreversibly degraded in underground applications such as drilling. The term "one particle" or "multiple particles" as used herein refers to one or more thin layers of particles, shavings, fibers, flakes, ribbons, bars, spheres, super rings, small balls, tablets or other suitable shapes with the following physical shapes. As the term "irreversible" used here, it means that degradable materials can be degraded in situ (such as in the drilling well), but will not be recrystallized or re-consolidated in situ (such as in the drilling well) after degradation.

這種降解可以尤其是由化學或熱反應(yīng)或輻射引發(fā)的反應(yīng)中所產(chǎn)生的。作為此處所用術(shù)語"一種聚合物"或"多種聚合物"并不暗示特定聚合度，例如，此定義還包括低聚物。可降解聚合物的可降解度通常少部分地取決于其骨架結(jié)構(gòu)。例如，在骨架中存在的可水解和/或可氧化的鍵通常能產(chǎn)生可以如下所述進行降解的材料。這些聚合物的降解速率取決于重復(fù)單元的類型、組成、序列、長度、分子幾何形狀、分子量、形態(tài)(例如結(jié)晶度、球晶尺寸以及取向度)、親水性、疏水性、表面積和添加劑。

This degradation can be especially caused by chemical or thermal reactions or reactions induced by radiation. As used herein, the term "one polymer" or "multiple polymers" does not imply a specific degree of polymerization. For example, this definition also includes oligomers. The degradability of degradable polymers usually depends at least in part on their skeleton structure. For example, hydrolysable and/or oxidizable bonds present in the skeleton can usually produce materials that can be degraded as described below. The degradation rate of these polymers depends on the type, composition, sequence, length, molecular geometry, molecular weight, morphology (such as crystallinity, spherulite size and orientation), hydrophilicity, hydrophobicity, surface area and additives of the repeating units.

另外，該聚合物所處環(huán)境如溫度、水分的存在、氧氣、微生物、酶、pH等會影響其如何降解。可降解聚合物的物理性能取決于諸如重復(fù)單元的組成、鏈的柔性、極性基團的存在、分子質(zhì)量、支化度、結(jié)晶度、取向度等幾個因素。例如，短鏈支化降低了聚合物的結(jié)晶度，而長鏈支化降低了熔融粘度并且尤其賦予具有拉伸硬化性態(tài)的拉伸粘度。

In addition, the environment of the polymer, such as temperature, presence of water, oxygen, microorganism, enzyme, pH, etc., will affect its degradation. The physical properties of degradable polymers depend on several factors, such as the composition of repeating units, the flexibility of chains, the existence of polar groups, molecular weight, branching degree, crystallinity, and orientation degree. For example, the short chain branching reduces the crystallinity of the polymer, while the long chain branching reduces the melt viscosity and especially gives the tensile viscosity with tensile hardening property.

該應(yīng)用材料的特性可以進一步通過共混、以及與其它聚合物共聚、或通過改變大分子構(gòu)型(如超支化聚合物、星型聚合物、或枝狀聚合物等)而修整。任何這種合適的可降解聚合物的特性(例如疏水性、親水性、降解速率，等)可以通過沿該聚合物鏈引入所選擇的功能性基團而修整。用于制備在地下應(yīng)用中有用的可降解顆粒(例如作為酸性前體、流體損失控制顆粒、導引劑、濾餅部分、鉆井液、水泥添加劑等)的常規(guī)方法尤其包括乳液法和溶液沉淀法。為了使用乳液法制備可降解顆粒，一般將可降解聚合物材料如聚(乳酸)溶解于鹵化溶劑如二氯甲烷中以形成聚合物溶液，隨后在充分剪切下向該聚合物溶液加入水和表面活性劑以形成乳液。該乳液形成之后，通過真空抽提或水蒸氣抽提將該溶劑從該乳液中除去，在水相中留下基本不含溶劑的聚合物顆粒。然后去除水，并通過離心、過濾或噴霧干燥收集顆粒。同樣，用溶液沉淀法制備可降解顆粒包括將可降解聚合物溶解在水可混溶的溶劑中以形成聚合物溶液。

The characteristics of the applied material can be further modified by blending, copolymerization with other polymers, or by changing the macromolecular configuration (such as hyperbranched polymer, star polymer, or dendritic polymer, etc.). The characteristics of any such suitable degradable polymer (such as hydrophobicity, hydrophilicity, degradation rate, etc.) can be modified by introducing selected functional groups along the polymer chain. Conventional methods for preparing degradable particles useful for underground applications (such as acid precursors, fluid loss control particles, guiding agents, filter cake parts, drilling fluids, cement additives, etc.) include, in particular, the lotion method and the solution precipitation method. In order to prepare degradable particles by the lotion method, degradable polymer materials such as poly (lactic acid) are generally dissolved in halogenated solvents such as dichloromethane to form a polymer solution, and then water and surfactant are added to the polymer solution under full shear to form a lotion. After the lotion is formed, the solvent is removed from the lotion by vacuum extraction or water vapor extraction, leaving polymer particles basically free of solvent in the water phase. The water is then removed and the particles are collected by centrifugation, filtration or spray drying. Similarly, the preparation of degradable particles by the solution precipitation method includes dissolving the degradable polymer in a water-miscible solvent to form a polymer solution.

以足夠的剪切將表面活性劑和/或水加入該聚合物溶液，以便該溶劑與聚合物溶液分離，留下基本無溶劑的聚合物顆粒，所述聚合物顆粒可以用已經(jīng)討論過的相同方法收集。與目前制備可降解顆粒方法相關(guān)的一個問題是表面活性劑和/或多溶劑的必要性

The surfactant and/or water are added to the polymer solution with sufficient shearing force, so that the solvent is separated from the polymer solution, leaving polymer particles that are basically solvent-free, and the polymer particles can be collected by the same method that has been discussed. A problem related to the current method of preparing degradable particles is the necessity of surfactants and/or multi-solvent

。乳液法和溶液沉淀法都需要使用不止一種的溶劑和/或表面活性劑。而且在這些方法中可能使用的鹵化溶劑會造成健康問題并且影響環(huán)境。因此，不需要使用表面活性劑和/或包括鹵化溶劑在內(nèi)的多種溶劑的制備可降解顆粒的方法會是有益的，并且更節(jié)省成本。

。 Both the lotion method and the solution precipitation method require the use of more than one solvent and/or surfactant. Moreover, halogenated solvents that may be used in these methods will cause health problems and affect the environment. Therefore, the method of preparing degradable particles without using surfactants and/or a variety of solvents including halogenated solvents would be beneficial and more cost-effective.